Generally, no.
no
yes it is!
No
A blank firing gun is completely legal in New York State, it is however illegal in New York City.
No.
Thompson contender
Approximately £200.
You can buy Thompson machine guns on Guns America. They have the Thompson 1927A1 .45ACP for around $1,100.
n0
No, you can own one.
I can't speak for all of them, but the blank guns I've seen will not because they have plugged barrels.