It depends on the country where you live so say 16 years others say 18 years old.
old enough to hold it up.
You can't. You will have to sell your old air gun, then use the money towards a new PCP air rifle.
Mis-use
Yes.
You will need to specify the use.
You don't need one. The darts which are made to use in air rifles are designed to be used in a standard, unmodified, breech loading air rifle. Just be sure the darts you use are the appropriate calibre.
yes it will not exsplode
Not usually. There are several factors involved besides the spring, but the .22 will usually use a stronger spring to propel the heavier pellet.
There are air rifles and there are air guns. These are guns that use air or C02 to fire a BB or Pellet, not gunpowder. A DAISY RED RYDER BB Rifle would be considered an "air rifle." There are several companies that make air guns and air rifles. Gamo, Daisy, Crosman, and Umarex are a few of these companies.
Yes, you do get to use Guns in the Air Training Corps (UK) such as .22 No8 Rifle and the L98 A2 Rifle and the L81 A2 Sniper Rifle In the Royal Canadian Air Cadets, Cadets are limited to using air rifles (the Daisy Model 853C) and I think on some occasions live firearms.
The rifleman as seen on the old TV series used a Winchester model 1892 rifle,or a reproduction of that rifle.
yes you can ---------------------- New Answer--------------- Only if the PCP rifle is designed for it. Most PCP's use Air but some are capable of using C02. Don't ever use or mix C02 and Air in the same tank. The tank must be emptied first before changing over to a new charging system (If it's designed for it.) The Marauder is one such PCP rifle that can use either. The Air Force Condor can use either but has a separate tank for air or C02.