There are couple of instances where if you go back (scroll back) you can change the outcome of the scene or have the game acknowledge that you did, i have four moment that came into mind:
The "who would you do"with Sophie : if you go back the dialogues gonna change and you can have a more romantic start (instead of naughty) with sophie. (it also impact dialogues with her in future interactions later into the game)
The "strawberry throw" with Jenni. By going back, here you can actually hit her mouth instead of missing.
The colour guess with Mia hair clip thingy. if you go back to try to "cheat", Mia will "prevent" you from doing so and tell you not to cheat.
And the "deja vu" moment with Sophie on the bridge. MC gonna comment that it's feel like a "deja vu" moment. I'm not sure how to proc this one but i know it's there because of URM.
edit: Oh and there is also the liminal corridor/space secret in the abandoned school of course !!!
( don't remember how to access it but somewhere in this tread i gave the solution , it's buried here somewhere lol. )
edit2: found it page 614(^^) :
for those who want to see and acces the easter egg : in the final free roam into the school spam click the right arrow until you are "teleported"
