The portal to progress was actually self explanatory. It's standard linear game logic after all. Follow the path get to the end.
I tried the rewind thingy while standing still to get a better look at it. I only noticed it turning red and move up my about one foot. Maybe I was looking at bad examples?
The movement especially on slopes was bad. I didn't get the grip I was hoping for to preform precise movement on. On flat surfaces and in the air it was tolerable, but slightly sluggish.
https://github.com/DaniDevy/FPS_Movement_Rigidbody it is very similar to your style of game.