My chain fell off. I put it back on and adjust the slack. I tighen all screws and now my bike is stuck and will not puch back or forth at neutral Why

Did you overtighten the chain? Also if you remove the spark plugs can you move the motorcycle in gear?

If you adjusted the slack, you had to loosen and tighten the rear axle bolt, at least on mine I do. Tighten too much? In Neutral, nothing is connected except the axle and transmission main shaft. I think you either tightened something too much, have done something wrong with the chain adjusters or are not in Neutral.

Remove Master Link if accessible. If it now moves, Wheel is locked up. Will it Move or start with clutch lever pulled in?