The VA garage itself is open most of the time because its used mostly for the VA (obviously), that said I don't know how strict SU is going to be about people who have VA passes for the fball games. Unlike the surface lots where no one is there until about 4 hours before gametime the VA will be manned pretty much the entire time. I am sure they will give some leeway but how much I can't really say. I can't speak to the alochol question 100% but from what I believe they don't allow any sort of tailgating once your parked and to be honest you wouldn't want to any.
Leaving can be extremely slow, there is an exit/entrance facing the dome but I don't think that is always open and even if it is both sides back up quickly and for a big game you can be stranded for a while. Both the garages in that area back up quickly when there is a big game or when most people leave at the same time so be prepared. I would recommend either hooking up with a post game tailgate or something of that nature until things clear out or try and leave a little early assuming the game is well decided. The two garages right there are great for parking close to the dome and keeping your car out of the weather but the downsides are no real ability to tailgate (unless your going to pass around some beers in the car but unless your 17 I am assuming thats out) and getting out can be a PIA. The 2 hour window would also concern me, I would test that out a bit for Clemson and see what you discover.
