Hey there thanks for the feedback and taking the time to play the game! I can give you some quick answers to the points you made!
1.1 This is intentional and is meant for people speedrunning the game and who like to go a bit faster. Its not like you have to do it. But I felt myself that I can speedrunning more fun if I add some other ways to move faster, I will not add a run button because that was already part of it in the beginning, but it had no real point was hard use with all the walljumping and diving. I am actually working on improving the movement controls and it will be updated for some future update.
2.1 In my opinion, it is pretty short already, but I can make the time u spend on a black screen a bit shorter, the animation with the music is in fact from the original source yes, so wont change that.
2.2 Thats just because the scene doesnt reset, and I dont see how it would improve anything to reset the cycle, u can literally just wait.
3.2 It may be different in celeste, but this game isnt similar in level design or movement physics. If you wanna compare it with other games, what about mario? Their Bounce pads also can be jumped on without instantly getting the full jump height, it just gives u the ability to time urself, instead of instantly bouncing off uncontrollably.
Thanks again for your feedback. I wanna make the game as good as I could possibly make it, and things won’t be perfect, but I want to work on it to make it more enjoyable for people, so feedback really helps.