In the United States, any citizen over the age of 18, as long as they are not convicted felons or fugitives from justice, may purchase a shotgun from a federally licensed dealer.
To get a gun license you would need to go into a gun store in the town you live in and ask for the information you need.
No state requires that shotguns be licensed.
You need to tell us more about the "gun license" and for what area. There are many different gun licenses.
Whether or not you can have a gun license at 20 years old depends on which US state you live in and the type of gun as the laws vary somewhat.
No.
21
18
How old do you have to be to sit in shot gun
That depends on if your state requires a license or not. Most do not.
Old enough to spell license.
It depends on where you are and what you mean by gun license. If you are in the U.S. and you mean a permit to carry a gun, check the related link for information.
1882-1907