1. Got it.
2. That's because the game is running in 60 fps.
3. Vanilla versions of them are kinda boring in my opinion, and also this decision was made at very start of development and I am not a fan of changing the game's fundamentals after so long.
4. "Always" high jump is frankly overpowered if you think about it.
5. I will think about it, thanks.
6. You are kinda not supposed to turn all of them off, but stages are beatable without one or two components being missing without changing the generation.