My understanding is that additional watersports content is on indefinite hold until the Payment processors get their collective heads out of their butts.  It's apparently one of the big no-noe's for whichever group kicked up a fuss that has itch de-spiceifying itself just recently.

Glory holes are at 'Sticky Steve's', the sex toy shop.  You don't find them immediately, I don't know if it is time gated or dependent on your level of Disinhibition, but I suspect it is the later.  They also show up as part of the Roommate's SO's challenges.

If the Harasser isn't exhibitionist, they won't be down to film their sexytimes.  If you really want to film your sexytimes with the Harasser, you will need to cheat the Exhibitionist trait onto them.

Not at the moment, the Roommate's SO being an abusive sack of shit is pretty much their personality.

Simple answer; yes, just talk with them daily & find out what their likes & dislikes are, then act accordingly.  Also, sometimes you get lucky & match their likes yourself.
More complete answer; yes, but it's not really worth it.  The Roommate is a 'scripted relationship', meaning your relationship is set to follow the Roommate 'story' & the roommate story in game is that your Roommate is 'that guy/girl' in your life.  It doesn't matter if you are friends or not, because a) they are 'whipped' by their partner, b) their partner is an abusive sack of shit, and finally, c) pretty sure they are set up as an incentive for your character to want to get into a different living situation ASAP.
All of this is my opinion as a consequence of consistent past interactions.

Check when you go to sleep & when you wake up, particularly when you wake up.  The scene fires off most frequently when you wake up at or near 7am.

Full day-time Exhibitionism may be possible once 'crime & punishment' is added, emphasis may.
Graduating is implied to be the 'end-game', I believe.  Year advancement is on the development roadmap.  I believe Anthaum wants to have finished up the first year's content before adding it however.

Depends on how you define 'best'.  If you are talking income generation vs. time taken, are playing on a PC so you can 're-roll', have a good Charisma skill, and start first day of game, making one vlog a day (approx 2.5 hrs) will net you between $75 & $100 daily after about a week or so.
You will have to do the lead in & maintain the daily output because anything over a week old on the site is automatically discarded.

If they have Exhibitionist, they will definitely be down for it.  If they have Slut, they might let you, but won't be happy about it.

Ok, this was a significant problem for me as well.  Here's what you do.  First, NEVER let your food need drop below 51%.
Second, when eating, pay attention to how many green arrows the food item has.  That is an indication of how much it restores your food bar.  As long as you are already at at least 51% full, any food that gives you more than you need will contribute to increased plumpness.  The 'cheap & easy' option is always choose Cheeseburgers, they have the greatest addition per serving of any food in the game.

If, for some reason, you have allowed your food need to drop below 51%, first eat something that brings it back up above 51% before eating the item that takes it over full.  If you are in one of the cafeterias, select multiple food items before 'finishing'.

Following these guidelines rigorously (particularly the 'never let your food need drop below 51%') will bring your plumpness back up.  Note, 'never' means even while asleep, always make certain you are full or nearly full before going to sleep.

Edit:  The final thing to be aware of, 2% is about the cap you will see for daily increase or decrease & that is only if you have gone to particularly extreme lengths.  Regaining plumpness doesn't happen fast.

First, is this on a mobile device or a computer, I don't have experience with mobile devices & this game, so all my advice will be for use on a computer.

That said; once you have used that button, check your downloads folder on your computer.  You should see a file labeled course-of-temptation-numeric string-numeric string.  That is your save file.

It's one of those hidden stats.  Mostly, you will see a message after you do something that increases it letting you know it went up.  I know that if you look into the underlying code, it will actually tell you what it is, but sadly, I am not a coder.

So...That's a LOT of questions.  I'm going to focus on the easy ones for now.  One thing to be aware of is that the game as a whole is more of a sandbox, than a definitive storyline.  You likely have noticed that it doesn't particularly advance beyond Freshman year at the moment.

1)  Yeah, once you complete the strike & get everyone's pay up to $15, the storyline is concluded.  There are likely individual scenes you have not experienced, but the storyline is done, at least until more is thought up & added.

2) I actually have not particularly advanced the River Rat past Senior Server, but, arguably even more so than Quickieburger, there isn't particularly much 'storyline' here.  It's a place to earn money & potentially have wild times occur.

3) More opportunities for Debauchery mostly.  The Party Popularity stat you might have seen mention of increases WILL be relevant to the next big patch currently being worked on by Anthaum, but that will go live when it goes live (i.e. when it's ready).  The Quad party exists so that the MC can blow off steam & recuperate for the next week of school.

4)  So, 'Favorite Date' is something that applies to any NPC the MC is getting serious with.  Basically, it just means the there is one specific date option they like best.  For NPC's with a particular personality, that 'favorite' date, might not even technically be a date.  Sometimes it's a booty call.  Note however, unless it's a booty call, it WILL be a DATE, not a hangout.  I don't know if the 'coffee date' option has become a favorite date for any NPC's, however.

5 & 6) This question is confusing.  I'm going to add 20 since they are all somewhat interrelated.  Each sport has varying degrees of storyline associated.  Football & Cheerleading are interrelated & basically just free-use cheerleaders after winning games, with a sub-'plot' of intra scholastic rivalry with another school's football team.  The 'being filmed having sex in a hotel room' scene is a plot by the rival team to demoralize your team mid-season.  It happens after winter break generally & only happens if you are on either Football or Cheerleading.  The swim team storyline is basically turning the swim team into a sex cult (I said what I said).  It continues well past naked swimming, keep going, sex will happen.

7) There is no 'storyline' per se for the Arcade.  It's an opportunity to make money & have uncomplicated sex once your Disinhibition & Exhibitionism are high enough.  (they don't have to be that high, either).

8 & 9) Again, there is no plotline associated with Streaming.  There are a handful of scenes that happen if you stream, but no plotline.  If you haven't already started naughty streaming, once you hit about 50% streaming popularity, you get an e-mail inviting you to start doing so using the same handle you use for regular streaming.  If you take it, your first Naughty stream will get a lot more traffic.  Streaming is one of the most reliable means of improving your Dancing skill (don't get me started on that rant, we don't have that much time...)

10)  I don't have answers to this one, I avoid that NPC like the plague.  (being their sub is not on my to-do list)

11 & 12)  The Admirer eventually invites you to their RPG sessions in the Quad mornings or afternoons (if you go in the morning before classes, there won't be one that afternoon), this eventually culminates in a scene in the game where you can push the relationship with them into D/s, & you can choose to be either D or s.  The Harasser relationship is complicated & multi-layered, because it will affect scenes outside of the classroom & in unexpected times & places.  If you go along with them, you will find yourself more & more submitting to them, with the possibility of eventually becoming their submissive.  If you don't, and are so inclined, you can flip the script on them & make them your submissive, but they are still pretty dominant-leaning, so they will be less 'submissive' & more... 'bratty', I guess.

13) At present, there are no events specific to any particular classroom buildings, no.  Any events that can take place on-campus, can still occur there however.

14)  Teachers/Faculty are ALWAYS going to say sexual/romantic behavior is inappropriate, at least where they might be observed.  Interact with them in their office.  You will get a message at the end of the interaction that will let you know if there is a point to trying to get sexual with them.  IF the message says something along the lines of 'you don't think you are even their type'  That means they aren't interested, yes.

15) Extra Credit scenes only happen from Extra Credit.  You can visit the Clinic now for condoms/other forms of birth control, but that's it.

16) That may be it for the moment.  The Library scenes are some of the newer ones, so there isn't as much variety as some others.

17, 18, 19)  Those I don't have answers for, sorry.

They are, but it is tied to a specific event path.  There is a box marked Hints in your sidebar.  One of the hints is regarding that very thing.  It's titled 'The Best Friend'.  Follow it's recommendations & you will get there.

It's you.  Do you know what world seed you used?

Yes, when the skill turns blue it won't improve any more that day.

While punching them could indeed be satisfying, I was actually thinking of something that would hurt even more, their feelings.  Something like getting right in their face with a comment like 'Did you actually see this playing out any other way?  REALLY?!'  Or the ones that go with something sexual if you fail get something like you shoving them up against the wall, getting right in their personal space & whispering in their ear 'Lets be honest with ourselves, it wasn't about the money, WAS IT?'  and then just walk off, leaving them with their failure & conflicting emotions...

As to the other, that would be great, but you (the player) has no control over what you (the character) picks in those situations.  I mean if we could start choosing, that would be great, but right now my Physical skill 10 Football player is always choosing vids about working out & his 'on the short side' English Major gf really has no interest, so maybe something about 'Nerd Stuff' or Dancing?...

Incidentally, thank you so much for putting the 'throw the match' option in, were you holding onto the making breakfast for the 'Official Relationships' expansion, or is it just more complex coding?

I have noticed when you try to shove past an 'Extortionist-in-a-Box' but don't have the Physical skill to pull it off, there are consequences.  Why are there no consequences for them when they clearly haven't got a hope in hell of blocking you?

Unrelated; when you are in a 'just chill' hang-out or date & you pick something to watch that reflects one of your interests but not theirs, is there a way to keep it from being something you choose later on with them?

So Who is everyone's fiercest Rival & why and how is it always Jacqueline Pierce?

'Tell me you've never encountered a woman in real life who's aggressive & willing to ignore social mores & boundaries without telling me you've never encountered a woman in real life who's aggressive & willing to ignore social mores & boundaries...'

Quickieburger, you have technically hit your max raise.  That said, keep working there & you will eventually meet the labor Organizer who is trying to get better pay for everybody.  That will lead to an event chain.  Here's a hint regarding the event chain; the Charisma, Physical & Exhibitionism skills will all be useful, so get them up now, rather than later.

The other stuff, I don't know.

The encounter with the Classroom Admirer, in the doorway of the Classroom after class; do they ever remember what they wanted to say?

Completely unrelated; if you decide not to go the trash human route with the 'Rich Kid' all the guys from his hall who previously seemed decent enough do a heel turn.  Do any of them not do that?  Like maybe if you have gotten their friendship up to actual 'friends' rather than just acquaintances?

Related to THAT; While I love that you now know what major an NPC has after interacting with them enough, will it ever be possible to add what their Residence hall is (even if it isn't yours) and who their Roommate is (again, once you have interacted with them enough)?

The Coaches for all the teams are modifiable.