I would argue it is incest. Masturbation implies you acting sexually with your own individual self. A clone/alt.universe you is not your individual self, just another being who happens to have the same appearance, thoughts and identical genetic makeup as you, like an identical twin but more identical. The genetic identicallity would make it incest.
Okay, but what about time travel in a stable loop? If you're only going back in time to bang past you because when you were younger future you showed up to bang you, what is that? It's the same you, but at a different point on your timeline.
No, because the hot dog bun is generally connected on one side making a folded V shape. It is a single piece of bread.
A sandwich must have two separate and discontinuous pieces of bread with the primary components in between them. So a hot dog is not a sandwich.