They do not, mainly because of the tolerances for paintballs themselves (it will burst when exposed to exploding gunpowder) and the size of them (the average size of paintballs are in the .68 caliber area), unless if you're talking about Simunition (in which this type of projectile is restricted to the members of the armed forces and law enforcement officers).
You can buy rubber paintballs, they are called Reballs, and any paintball gun can shoot them. The police and militairy also have several specialized or modified guns to shoot them at higher FPS.
no, paint balls are several times larger than air soft bb's
without CO2 or paintballs, you just put the bolt forward. In most guns this is how you de-cock after a day of play, but if you have a regulator, it may store a single shot. If you fire without co2, the gun will not cycle or fire a paintball, it will only go into the barrel. If you fire with no paintballs and co2, you may damage your gun.
It would probably work, but it would ruin some part of your gun. You could freeze the paintballs if you wanted to. That would work just as good as a marble.
paintballs
Do you mean a firearm or a paintball gun?
No, paintballs can vary in size depending on the type of gun being used. It is important to use the correct size paintballs for your specific gun to ensure proper performance.
Yes, however you wont feel a blast of air further than a couple inches from the barrel
No, most fields won't allow the 6mm paintballs used in airsoft/paintball hybrid markers; definitely check with your field before bringing any.
No. Paintballs are much MUCH larger than airsoft pellets (.50-inch and higher), the guns' feed mechanisms are completely different.
not very long
around 25.