I have 2 20-inch bmx wheels but one is blocked and does not respond when I pedal and the other works but not much works I can't pedal much but I want to know if they can fix it

Honestly, I would get a new set, and use the bad ones as an opportunity to learn how to tear down, and fix your old parts at home, but yes, aside from them being scrap metal, they can fix em.

Yes they can

I believe so haven't been there myself but worth a try