No, because there is no double battle in the elite four
well, i used swampert, pikachu, groudon, gardevoir and medicham and swellow all level 47-52 :)
No.
yes
I don't know what Pokemon you have, but i beat the Elite four with just Swamper level 59 (grew to 62 when i was done with them) and Gardevoir level 50 (grew to 51 after) Swamper- ice beam, earthquake, blizzard, muddy water and Gardevoir- confusion, psychic, hypnosis, thunderbolt. Those were the only ones i raised through the game to Elite four. Hardest one was ludicolo on Wallace. Other than that, no problems.
no
no
Beat the elite four
NO (only on ruby)
battle 8 gum and beat elite 4.
Blaziken, Kygore, Groudon, Raquaza........ with an high level.... and a electric type Pokemon that knows electric moves.....
If this is Emerald get Raquaza and Kyogre and also get Groudon then you beat the elite four with those three plus the Sceptil.
first you beat the elite 4 then go to meteor falls on route 114, go to steven and battle him, groudon will apear if you beat him