1) Yeah, I was exiting the level through menu, then launched the level again, not sure if I reached any check-point, after death I was spawned at much later check-point.
Wasn't able to recreate that bug again, I probably touched previous checkpoints a lot. (only overriding check-point vid) https://files.catbox.moe/apa9dz.mp4
2) You probably could calculate needed speed with distance, point of connection through code, but I just cut every platform that needed syncing ;)
3) I played the whole game with this speed XD https://files.catbox.moe/pz5pea.mp4