I don't KNOW the answer to any of your questions, but I can make some guesses.
In Las Vegas, a pretty fair number of the gunshow exhibitors are from California. If you want to buy something, the gun has to be transfered to a Nevada dealer. There is one dealer there that does nothing but transfers and the paperwork on all guns sold at the show. That's right, every gun sold at the show by a dealer goes through him and you have to pick it up the following week at his shop.
Based on this I would imagine that there will be plenty of California dealers at a Reno show considering it's proximity to California. I would imagine that if you wanted to buy a handgun, it would have to be transfered to a California dealer or if the dealer happens to be from California you would have to pick it up at their shop with all applicable laws enforced. By the same token I have no idea what the laws are regarding the purchase of guns by out of state residents. I am almost positive that you can not buy a handgun out of state although I imagine it could be transfered to a dealer in your state, and I am sure that all laws regarding a purchase in your state apply. I know it used to be that long guns were OK for purchase by a non-resident, but I recently ran into a problem trying to buy a shotgun in Ohio. I was told that they can only sell to a resident of a state bordering Ohio. I don't know if this is a federal law, a state law, or the guy didn't know what he was talking about.