Yes, any nitrogen tank is refillable.
yes they are refillable
Yes, in-fact only pin valve tanks are refillable. Ones with a non resealable top can't be refilled.
Yes they are the same.
yes, to any gun made in the last 15 years
Yes, Tm7s can run on HPA tanks.
High pressure air, and all air for that matter, is about 78 percent nitrogen, so it is nicknamed a "nitrogen tank" . So a HPA tank is supposed to be filled with "nitrogen" which is really just air.
Cubic Inches or the Volume. The Bigger the CI the more air its holds.
Pure energy (PE) manufacture steel tanks that have a PSI rating of 3000. and also make aluminum-carbon fiber wrapped tanks that have PSI ratings at 3000 and 4500P
In addition to pressure, all tanks have a volume rating, which is the volume of air at standard pressure that they contain - most 3000psi aluminum tanks are aluminum 80's, which are 80 cubic foot tanks, but they come in sizes from 2ft.^3 for a pony bottle to 130 ft.^3 steel tanks, and sometimes even larger.
There are non refillable, disposable cartridges that range from the standard 12 grams to 4 oz. There are also small refillable 45 butt stock tanks and other small and long tanks like it. After 4 oz, a tank must be fitted with a "burst disk" which allows it to bleed out if over pressurized. Any refillable tank over 2 inches in diameter needs to be hydro-tested every five years.
Call them and ask!
No, you must have it refilled at a paintball field or pro-shop. You cannot refill paintball tanks from low pressure Soda dispenser C02 tanks.