Not in the United States
There are licenses and licenses. You can get a firearms owner's ID that will permit you to purchase and possess a rifle, shotgun or bb/ pellet gun at 18. A handgun permit is 21. A permit to CARRY a concealed handgun is 21.
No
bb guns.org
Which model
In most cases it will be a BB gun. But Pellet guns exceed both the BB and the airsoft guns. Pellet guns can attain speeds over 1200 FPS.
First, check to see that you have a BB gun, and not a pellet gun. Both pellets and BBs are made in .177 cal. A pellet gun will not shoot BBs (in most cases) If your gun IS a BB gun, you will need a gunsmith to check it for damage, stuck items in the barrel, etc.
It may cause problems with jamming. It is not recommended.
Actually a BB gun is an air gun. But an air gun also includes pellet guns and rifles. BB guns are the bottom end of the air gun family. Pellet guns are more accurate than BB guns and they usually cost more.
Air rifles use compressed air or C02 to propel the BB or pellet. They do not use gunpowder. Their is no bullet shell and bullet just the BB or pellet.
Colt makes a 1911-A1 Pellet gun made by Umarex. I know of no BB gun unless you are asking about an Air Soft gun. The Pellet gun is very good. I can not answer about an Air soft gun.
Pellet guns are more powerful. They are stronger because they use a CO2 Gas, whil BB guns are spring-powered.
You Don't. Shooting BB's in a pellet gun that is not designed for it will ruin the rifling in the barrel. Some airguns are designed to shoot both BB's and pellets. But if the Owners manual calls for pellets and says nothing about BB's then stick with pellets.