Go to the ferry in snowpoint city and play in the battle tower or get all the legends your choice
You finish the Pokemon league and get the national pokedex You finish the Pokemon league and get the national pokedex
finish the pokemon league
finish the Pokemon league and go to the spring path you will see a new cave go in the cave it changes so just wander
the best Pokemon for the Pokemon league is definetly latios
you have it!
In Pokemon League
beat the league and he will be gone
there are none that i know of in diamond. sorry(-_-)
finish Pokemon ranger (1) and input the special manaphy code and finish the mission and trade with diamond (must have 2 ds)
I beat the league on Pokemon Diamond version, and there was no cave involved, if that's what you were asking.
finish your pokedex
near the Pokemon league