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.
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.
Yes they are the same.
yes, to any gun made in the last 15 years
Yes, Tm7s can run on HPA tanks.
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