nothing. just the Pokemon migrated will not go back to ruby.
you can't get the black flute in leaf green but you can in Pokemon ruby, sapphire and emerald then trade it to leaf green.
You can't migrate from HeartGold to Ruby. But it can be the opposite. Pokemon can be migrated from Pokemon Ruby to Pokemon HeartGold.
they go to the palpark.
It is in the wild, anywhere. Whenever you change location (go into houses, etc) it will change place. You need to 'unlock' it before you can get it though.
Migrated Pokemon are the ones you can catch at Pal Park after you transfer them from FireRed, LeafGreen, Emerald, Ruby or Sapphire games for the GBA.
ABXY
Sadly, no. The creators of the game forgot to add in the Pokedex, so trading is impossible without GameShark. :(
You can only get groudon if you migrated it through the pal park from Ruby or Emerald.
You use the pokémon that were migrated from either Ruby/Sapphire/Emerald/Fire Red/Leaf Green.Any pokémon that you had in those games can be migrated and caught in the Pal Park.
use action replay
Ruby Murders happened on 1920-02-27.
Ruby Ridge happened on 1992-08-21.