It depends on where you are. In the U.S. federal law requires you to be 18 to purchase a rifle or a shotgun from a dealer and 21 to purchase a handgun from a dealer, however, many states allow people 18 or older to own handguns, you just can't purchase them from a licensed dealer. None of that involves a special permit, however, except for the state of Illinois, where anyone who wants to purchase a gun must have a Firearms ID Card.
People under 18 however, can possess guns under certain circumstances. Target shooting or competition, etc.
No permit required.
It depends on where you are. Most U.S. states don't require a permit to own a gun. In order to carry a gun, you need a permit in some states, but each state sets its own laws on how to get a permit, so it depends on where you are.
Most likely YES. In some states and countries they are not legal to own
It depends on where you are. In the U.S. you can own a gun in any state without a permit, except that the state of Illinois requires an ID to purchase a gun.
No.
No, although handgun purchases do require a purchase permit.
It is not illegal. There is no permit required to own a firearm.
It depends on what you mean. In the U.S. to own a gun, you don't need a permit to own a gun except in a very few places. If you want to carry it, it depends on where you are. Each state sets its own rules for that.
No. You need a special permit.
Yes if you have a gun permit.
It is not illegal to own ammunition but you must have a permit to own a gun.
Yes. You can have a loaded gun in your own house or on your own probably basically anywhere in the U.S.