Yes.
Far too many (thousands) to list here- license requirements vary from one place to another. We cannot answer without knowing your country or state.
If you are 21 and have no criminal record there is no requirement to have a carry license however you do need one is you wish to carry concealed.
yes
No it's not necessary.
A gun shop.
Yes
Gun shop, gun shows, internet auction.
try gun shops and gun shows.
Yes, Here in Canada the law is 500 fps and under. I would check around to see yours.
No.
no
Impossible to answer without knowing the caliber.