Yes. without rails there is nothing to mount the scope (and scope rings) to.
Truthfully, You don't really need an optical zoom site. A red dot is the most you need for paintball. Paintball markers arn't accurate enough to utilize a optical zoom site correctly.
In paintball there is very little use for magnifying crosshair scopes. The greatest magnification you would ever need is a cheap 4x scope, and that would only be accurate for a few guns, with impeccable paint to barrel match. The only guns that could use a scope accurately are the T4 first strike, and the SO longbow. Most "snipers" use red dot or reflex sights, because it allows you to show where your shot will go(as accurate as paintballs can) and will not give you tunnel vision. Some scopes also cannot work with a paintball mask on.
There are no "good" scopes for that price. If you haven't the money to buy a decent scope, odds are you don't need one.
Yes, every few games, you will have to refill the tank, depending on the size. Without it, there is nothing to propel the paintball.
You could try out at http://riflescopepro.com. They have a vast range of scopes for every need.
You would need zoning permits and insurance to open a paintball field.
you need Co2 to fire any paintball gun, it is what physically moves the ball out of the barrel.
No, all paintball hoppers have a standard neck size.
Paintball gear is what keeps you safe in paintball. The mask is the only truly crucial piece you need to play paintball (meaning you can walk onto a field without a gun, or tank or paint).
Yes. A paintball gun is not considered a firearm therefore a felon can purchase a paintball gun in Texas.
no. only if the title of your paintball marker says "electra"
A paintball gun needs CO2 (or HPA) to fire at all.