Federal law to purchase is 18 for long guns and 21 for handguns.
Three.
You need to tell us more about the "gun license" and for what area. There are many different gun licenses.
If you're referring to a concealed handgun permit, yes, Texas grants recognition to Indiana CCWs.
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
That depends on if your state requires a license or not. Most do not.
You have to be 12 years old, with a boating license. If you have a valid drivers license (16+) you can drive it. :)
Old enough to spell license.
Mopeds do not require a 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.
you can be 10 but you need a hunters license