Air Rifles vary a lot, you want enough ft lbs energy for a clean kill. 6 ft lbs is the minimum for a squirrel air guns rated for hunting will do that. 15 lbs is generally considered adiquite for Rabbit - most magnum class .20 - .25 are good enough for them. 40 ft lbs is a good minimum for racoons very few small bore air rifles can deliver this much energy but large bore (greater then .25 cal) can do this with ease. One that can take raccoons should work fine.
The Quakenbush Outlaw is a supreme hunting air rifle delivering 500 ft lbs. It has been used to take down wild bore and even larger game.
The other thing to consider is range, Pellets have a very low BC compared with fire arms which means they loose power faster. If you have an air gun that delivers 25 ft lbs and do a head shot at less then 10 yards you will most likely make a clean kill but at 50 yards most likely not.
Consider a .22 short has about 35 ft lbs and is a poor choice for a large raccoon even at close range.
A 22 lr has about 125 ft lbs which is a pretty good choice for fox hunting.
It depends on the power of the air rifle, Local laws and the location where you live.
Yes
Yes:
No.
Any caliber higher then .22 Long rifle should the job But a .38 should work fine.
It all depends on the rifle, pellet and power source.
Depends on the rifle. Accurately? About 50 yards max.
Depends on where the backyard is located.
yes
yes, if you are in space at the time and have an air rifle, you shoot it out the window, you die because of the vacuum, but it is successful. you killed yourself but got a BB pellet into space. WEAR a helmet next time.
no it is extremely unlikely that is possible
Not anywhere in the US that I am aware of. Do understand that an air rifle, from a certain distance, looks like any other rifle so don't point it at cops or they will shoot you.