Too many
You need to define the term gun license. In most of the US there is no license to own a gun. Some states require a license to carry a gun. others to carry a gun concealed. There is also a license to make or sell guns. All are different and have different procedures.
You need a license to carry a firearm in many places. You cannot carry one on an airplane.
Yes- that is the whole purpose of a concealed carry license.
In states that require them, it is a license to own (not to carry concealed) a gun.
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?
There is no such thing as a gun license in the US. There are concealed carry permits/licenses and dealers licenses.
You can apply but not only will you not get a license to carry, you will not be issued any firearms license.
If you mean a handgun carry permit, you can't. Illinois does not issue gun permits.
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.
It depends. Some, but only a few, states in the U.S. require a license to purchase a gun. A gun permit normally refers to a permit allowing you to carry the gun on your person in public. Some people use the terms interchangeably, but each state calls the gun permit something different. In Tennessee, it is called a "Handgun Carry Permit." In Florida, it is a "Weapons Permit."
With a license, yes.
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.