I used the walk through walls cheat 72BC6DFB E9CA5465 A47FB2DC 1AF3CA86 509197D3 542975F4 78DA95DF 44018CB4.While on the ice try to get to the top left part with cheat disabled, after getting there then try to get to top right side then you will find Groudon.Boring part is that you can't battle it yet but you should take the item behind it.The item is the poke ball that contains Mewtwo which carries mega stone for y version which will help when you obtain mega bracelet
P.S if you disable cheat while on top right side of ice you will be stuck as the player cannot move in that side
P.S if you disable cheat while on top right side of ice you will be stuck as the player cannot move in that side