Actually Pokemon Omega Ruby and Alpha Sapphire is not out yet, but I strongly believe Bulbasaur will evolve at level as usual I doubt it would change dramatically.
You can catch Skitty in Pokemon Omega Ruby and Alpha Sapphire in the barks of trees.
Illumise in Pokemon Omega Ruby can be caught in Zorua at the park.
Minun can be caught in Pokemon Omega Ruby by seeking out these powerful Pokemon and then unlocking their incredible potential.
You can catch them like suicune,raikou,and entei after you completed the National Dex or you can trade them from other games.
You have to transfer it from your Pokewalker. You get it on Icy Mtn. Road.
Catch It In Cinnabar Island
Plusle can be found and caught on Route 110.
There are some Kalos region pokemon available in Omega Ruby and Alpha Sapphire such as Skrelp and Clauncher. More are available in Pokemon X and Y.
Bulbasaur is not in ruby you must TRADE him to get him
Yes you can in the place can catch kecklion invisible just walk around for about 3 hours you find him you need the second pokedex
One way you can catch Pikachu in either Pokémon Omega Ruby or Pokémon Alpha Sapphire is that you can find one to catch in the Safari Zone additionally you could have someone else catch one for you and trade one of your common Pokémon for it and you could also use one of your previous Pokémon games and catch Pikachu in one of those games and then transfer it over into either your Pokémon Omega Ruby or Pokémon Alpha Sapphire game.