Depends on the connections.
If it has threads on the top, you refill it like any other tank by taking it to a sporting goods store or paintball field. If it does not, then it is a disposable, and you cannot refill it.
Dicks, any paintball shop, and Gander Mt.
sure, gennerally there are 30lb co2 tanks and 50lb tanks that you can fill from, you will also need a fill station and instruction from a air smith on how to use it, so it is fairly expensive to own, but what a lot of people do it buy a fill station and then rent a co2 tank for the day from a welding shop or another place that will do it (scuba shops sometimes, propane stations, you just have to do a little searching) for a 50lb tank i think it was around $30-$40 so have everyone pitch in a few bucks and you are covered for the day
~$30
"H" is not a size for CO2 tanks
If you are not trained on filling Co2 tanks (unlike HPA tanks) you should not attempt this, on risk of breaking the burst disks, or freezing your hand. An HPA tank however, you can simply hook up and fill.
No
Last I checked sports authority does not fill HPA tanks. If you are looking to get a tank filled though I would not suggest going to sports authority unless it is your only option. I used to work at one and the employees there really do not know what they are doing when filling tanks and you would be fortunate to get a half full tank when you walked out.
No, paintball co2 is much higher pressure.
Yes, every few games, you will have to refill the tank, depending on the size. Without it, there is nothing to propel the paintball.
It just depends on the tank size, temperature, gun efficiency and how much you shoot.