Well, as far as starting, you'll have to figure that out or give us some more info. Does it have spark, fuel, air?
As far as the sprocket moving, you will see it move, even in neutral without a chain on it. There will always be a little friction there. Does it have a chain on it? If it's pushing the bike in nuetral, make damn sure everything in the tranny is right.
Did you figure out why 5th blew in the first place? That's what would scare me