First of all you need to state where you live. The law is different, depending on the country where you live. Are you asking about metal BB's or airsoft BB's?
No it's not designed to do it.
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.
yes
Put in the magazine. load the magazine, and shoot.
18 to purchase
Probably not- that is a LOT of BBs. What does the manual for your gun say?
No recommended, Not designed for plastic BB's.
No, if you are talking about bb's for a BB gun. The BB's for an air rifle or BB gun wont even stay in a Magazine for an airsoft gun. Airsoft BB's are 6mm, air rifle bb's are much smaller. You will ruin an airsoft gun with the smaller metal bbs. But you can get aluminum 6mm pellets for an airsoft gun.
You must be 18 Years old to purchase one
Nope. Plastic BBs are 6mm- about ,24 inches. Metal BBs are smaller- about .177 inches.
.12 gram bbs.
pellet=no bb's= 6mm plastic not copper.