Arceus is not obtainable in Pokémon X and Y, and thus you must transfer it from any Generation V game (Pokémon Black, White, Black 2 and White 2) through the Poké Transporter once the Pokémon Bank is released in December 27th, 2013 or ask someone to trade you one after this date.
It's currently unknown if there's going to be an Arceus' give-away event for Pokémon X and Y.
In Pokémon X and Y, the Chamber of Emptiness is where you can find the Banettite, which is the Mega Stone for Banette, and the Spooky Plate for Arceus.
Pokemon X and Y cannot trade with Diamond, Pearl and Platinum.
There are currently no known upcoming events for Pokemon involving Arceus. It is possible there could be an event for Pokemon X and Y or Omega Ruby and Alpha Sapphire but there seems to be no plans as of yet.
*Mew is not catchable in Pokemon x and y, but you can get him online from wondertrades and such. Mewtwo however, is catchable and you can find him in the cave in pokemon village.
Parfum Palace. Find the owner's Furfrou and he will give you it.
Dive is no longer a TM or a HM in Pokemon X/Y. You'll have to have a Pokemon learn it naturally.
That's unknown. Arceus is already too strong as it is now, it doesn't need a Mega Evolution, and holding a Mega Stone would prevent the use of the Multitype plates anyway.
Yes You Can Get A Pikachu In Pokemon X and Y.
Arceus is not obtainable in Pokémon X and Y, and thus you must transfer it from any Generation V game (Pokémon Black, White, Black 2 and White 2) through the Poké Transporter once the Pokémon Bank is released in December 27th, 2013 or ask someone to trade you one after this date. It's currently unknown if there's going to be an Arceus' give-away event for Pokémon X and Y.
The Legendary Pokemon available in Pokemon X/Y are:Xerneas (X only)Yveltal (Y only)ArticunoZapdosMoltresMewtwoZygarde
You may be able to find someone to trade a Special Torch for Pokemon C or Y in a Pokemon Facebook group.
Pokemon X and Y are sold at MSRP of $39.99 (CAD)