That depends on if your state requires a license or not. Most do not.
You need to tell us more about the "gun license" and for what area. There are many different gun licenses.
you can be 10 but you need a hunters license
That depends if your state requires a license. Most don't.
You don't need a gun license if you are 25 but if your under 25 you do need a gun license
It depends on where you are and what you mean by "license." In the U.S. in most states, you have to be 21 to get a handgun carry permit. In most states, you do not need a license just to own a gun.
You never need a license to have an Airsoft gun.
You need to contact your local authorities.
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.
yes
No.
It depends on several factors; Where you are located and exactly what you mean by "gun license." Do you mean a license to carry a gun? A license to purchase a gun? A license to build guns?
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.