Not in general but if u get caught u probably get in trouble.
No There is not
It depends on where your backyard is. If it's your backyard and you are in a rural area, you should be OK. But if you are in a less rural area, there may be laws against discharging projectile weapons like BB guns, arrows, and paintball guns.
The owning and operation of a paintball marker does not require any permits.
No, there is nothing that can do that.
There is no record of any Incan sport of "paintball"
Yes, any material will reduce the impact of a paintball.
yes, to any gun made in the last 15 years
Just type in paintball to any search engine, and find a paintball field near you.
There are no "child" paintball teams anywhere.
any where on the internet
There is no reason to put a paintball gun in a refrigerator, or any appliance for that mater.
There are no "kids paintball teams" anywhere.