well it depends what kind of projectile you are useing. to me it would sound like you are useing a air-rifle, anyway what every you are useing and i dont know why you want to what you want to do but just make sure you get a clean kill :)
Yes: small game. Rats, squirrels and small birds.
Yes. I suggest hollowpoint pellets and a head shot. This is the best and humane way to put down the animal
Yes it is possible
yes i have killed possoms with a bb gun
Depends on the FPS. If the gun is over 400 fps it can go threw a can. My friend has a 400 fps ak 47 and it can kill the can.
Yes they are safe to be used in airsoft and can withstand almost 750 fps (i tried an expirament with my goggles and my friend had a 725 fps gun and shot my goggles to see how tough they were and they held pretty well.
350FPS would be sufficient
No, a pellet gun can't kill a bear it will only make it angry. There for it will eaither attack you or just ignore it.
Depends on what you are trying to kill. A small rodent, then Yes. A larger animal then most likely NO.
the most fps in a gun is 500 or more and my best gun is a mp44 because its 517 fps and it hurts and it feels like a bb gun
500 fps
250 FPS