In snowpoint city at the bottom there is a sailor that recognizes you as a good trainer and takes you to the fight area after you beat the elite 4
Beat the Eliet Four and then the miner dudes will go away and Pal Park will be open
bring any level 100 Pokemon from diamond version or train a Pokemon to level 100 and go defeat them.
once you get all bADGES AND BEET THE ELITE FOUR
he is in the woods
train your pokemon to level 60+ and fight them...
you don,t have to to defiet the eliet four again
i only know what to do in the diamond and pearl. after you defeat the elite four, go to snow point city and talk to the guy with the boat. he will take you to the fight area on battle frontier island.
beat the eliet four if you havent
when you beet the elite four you find themon the rock map
You can catch Riolu in Challangers cave. You can't enter challangers cave till you have beaten the eliet four at least once.
-mongmong908
You can find out how many times you have beaten the Elite Four in Pokemon Diamond by checking your PC in the game.