yes, most green airsoft bb's are biodigradable
Airsoft bbs are made up of plastic and are 6mm in diameter and are .24 cal, BBs however are metal and are .177 cal (4.5mm)
Type recommended by the maker of the airsoft.
The stinger p9 is good with .12 gram airsoft BBs or you can use .25 gram bbs but then it will decrease the range.
you can not use metal bbs in airsoft guns at all. they are not compatible because they are both built differently.
yes they are very accurate
.25 Airsoft bbs can be good. Their weight is very good for accuracy and helps for a harder hit from the bbs. However, no bb is good if they are not high polish. Companies like Madbull and Matrix make good .25 bbs.
standard 6mm plastic bbs.