There's the elite four cave you beat the elite for then get the national Dex and the cave were the big persons standing hes gone and you go throw there and theres a girl you go on untill she goes ans you surf in the water and then you find a lapris  (NO CHEATS NEEDED)

You have to beet the elite four then get the national Dex. And have the lustrous  orb and shiny orb. Ask for shaymin next