No!
No.
Not normal ones but at your local sporting goods store there should be some if not no.
No not all of them are. They have to say biodegradable on the bag when you buy them.
you can not use metal bbs in airsoft guns at all. they are not compatible because they are both built differently.
yes because 0.20 and 0.2 are the same even if its air soft guns
yes if it fits but metal bbs cans destroy the rifle
No
All airsoft guns can shoot .12g bbs. However with more powerful guns, heavier bbs are recommended for better accuracy
Yes it is possible but rare.
1
Not recommended, ever.