I don't know what you mean by ajusted, but the power of it can definitely not be adjusted (in any airsoft pistol I have ever heard of) unless you buy new parts for higher gas flow, and the hop-up probably can't (if I am looking at the same gun you are). The sights also cannot be adjusted, if that is what you meant (again, if I am looking at the same one you are).
No you do not need to put air in an airsoft gun. These guns are either spring powered where you must cock the gun before you shoot it, electric powered which are automatic and require batteries, or CO2 powered which requires a CO2 cartridge. This CO2 is not expensive and a pack of 40 CO2 cartridges costs only 20-25 dollars. the guns that require CO2 are not as common as the other forms of airsoft guns, although they are more powerful. In general, if you buy an airsoft gun, you do not need to put any air into it.
Usually, the only non electric rifle this is also automatic will be CO2 powered.
Read the directions for YOUR gun. CO2 does not explode, but may leak down.
Define real? If you mean like a actual gun which shoots bullets, no. If you mean real as in not fiction, yes. There are several CO2 powered rifles, such as the Beretta CX-4 Storm which is powered by a 88 gram CO2 cartridge.
An air-soft gun that is powered by CO2 or green or red gas instead of a spring or a battery.
Your best bet is to look at airsoft products. Most of them are powered electrically, but there are plenty that use co2 or green gas to operate.
The best full metal blow back CO2 powered airsoft pistol is the U.S. Army Duty Calls Elite 1911 Full Metal GBB Airsoft Pistol. A close second is the 500 FPS Full Metal M87, Sport 301L.
Any airsoft weapon shout be cleaned regulary in order to work stable and for long time. Especially if you play in harsh environment like dust, sand or dirt.
no
There is no technology supporting CO2 powered vehicles at the moment.
yes
Most all teams allows virtually all types of guns. The question is what fields are the CO2 guns allowed.