He should digivolve into Minomon or Tanemon at level 3. I'll take a look at it when I get a chance.
I think I made him a trade evolution for now, but he shows up between Pewter and Mt. Moon if you want to catch him.
I answered the veemon question a few posts ago. The rest of those digimon aren't in the game yet.
Read the DNA Digivolution section to see which digimon DNA digivolve. Once you have one of the pairs go to Gennai's lab and talk to the assistant in the same area as Gennai. He should be standing next to a big machine on the left side of the room.