The starter Pokemon for Alpha Sapphire and Omega Ruby are the following:
Torchic (Fire)
Treecko (Grass)
Mudkip (Water)
As to which is best to choose, that's a hard one. There are an awful lot of water Pokemon in both games, so if you want to have an immediate advantage, then you might want to go with the Grass option. However, with Wonder trade in the new games, it will probably be easier to trade for the other starters, so it's probably just fine to pick whichever one you think looks the best. :)
No, you will need to trade for them or transfer them via Pokemon Bank to get them in Pokemon Omega Ruby and Alpha Sapphire.
No, there are no roms for Pokemon Omega Ruby and Alpha Sapphire currently nor a working 3DS emulator. (They are also incompatible with the Desmume emulator.)
No. Pokemon Omega Ruby and Alpha Saphire are remakes of Ruby and Sapphire, from 3rd Gen. Omega Ruby and Alpha Sapphire are in the same generation as X and Y, 6. Hope this helps you.^w^
You have to transfer it from your Pokewalker. You get it on Icy Mtn. Road.
It evolves by happiness
Mudkip is available as a starter pokemon in more than one games. They are Pokemon Ruby, Pokemon Sapphire, Pokemon Emerald, Pokemon Omega Ruby and Pokemon Alpha Sapphire.
You can catch Skitty in Pokemon Omega Ruby and Alpha Sapphire in the barks of trees.
Yes, Tm's in Pokemon Omega Ruby and Alpha Sapphire are re-useable
No, you will need to trade for them or transfer them via Pokemon Bank to get them in Pokemon Omega Ruby and Alpha Sapphire.
These Pokemon can be found before the National Dex: Latias (Alpha Sapphire), Latios (Omega Ruby), Kyogre (Alpha Sapphire), Groudon (Omega Ruby), Regirock, Regice, and Registeel. These Pokemon can only be obtained in the Delta Episode: Rayquaza and Deoxys. Post-National Dex Legendary Pokemon are: Regigigas, Ho-Oh (Omega Ruby), Lugia (Alpha Sapphire), Heatran, Mesprit, Uxie, Axelf, Palkia (Omega Ruby), Dialga (Alpha Sapphire), Giratina, Cobalion, Terrakion, Virizion, Reshiram (Omega Ruby), Zekrom (Alpha Sapphire), Kyurem, Raikou, Entei, Suicune, Tornadus (Omega Ruby), Thundurus (Alpha Sapphire), Landorus, and Cresselia.
No
It is not yet known if there is a building location for the GTS in Pokemon Omega Ruby and Alpha Sapphire.
The ability of Mega Diancie in Pokémon Omega Ruby and Alpha Sapphire is Magic Bounce.
Yes, all the TMs that were in Pokemon X and Y will be available as TMs in Pokemon Omega Ruby and Alpha Sapphire.
No, there are no roms for Pokemon Omega Ruby and Alpha Sapphire currently nor a working 3DS emulator. (They are also incompatible with the Desmume emulator.)
all of them
There is none