Yes. You can buy a gun through a private sale or gun show.
The state of Missourid does not require registration, so the answer is, you don't register it.
To buy, ou have to be 18 for long guns and 21 for hand guns.
Federal law says you have to be 18 to buy a long gun and 21 to buy a handgun. Find a lawyer familiar with firearms law to get a correct answer to your registration question.
You would have to go to your local gun shop and register your firearm there. Then, after completing that, you would have to go the gun range and register yourself there, with your gun permit.
Depends on where you are. In MOST of the US, there is no requirement to register an ordinary firearm. There is also no place to register a gun- on line or otherwise.
Depends on what state you are in. In MOST of the US, there IS no requirement to register a gun.
That would depend on where you purchased the gun and what the local laws are. If you purchased a gun from a private seller it would be your responsibility to register it. If you purchase from a gun store, they probably register it during the sale. However, only a few states require registration. So the answer is, you probably don't have to register the gun, regardless of where you bought it, unless you live in California, Massachusetts, or one of the other states that require it (there are only about 5 or 6 states that require registration).
No
No.
no
No