Best solution - is to have rule to lock FPS to 60 OR to add "In-Game Time" for some runs with in-game timer available

So, Redline Edition records should have timer, and Classic CrashDay can use built-in timer, because it is not bugged here.

I don't think so.

If Alt+ Tab will get restricted from individual levels - there is no reason to have "Score the most stunt points in ##:## time!" missions there, since everybody will have the same time. But, as you mentioned, its based on luck, and that's pretty unfair IMO. So i think, we should restrict doing that, and remove Amateurs1 and Finals2 from here sicne they will have no sense.