which island do you mean?
get thegost glinch
The Battle Factory is unavailable in Diamond or Pearl, but it is in Platinum, Heartgold, and Soulsilver.
NO. To unlock the rest of the island, you must complete the whole Sinnoh Pokedex and beat 7 trainers at battle tower on Double Battle mode. - The Man In The Trees (The Pokemon Expert)
iron island
you have to get there by boat
You can't only in Pokemon Platinum unfourtunatly.
NO! You can only unlock pal park on platinum, diamond and pearl
you cant
You have to go to it but nothing happends
iron island but have some Pokemon that have HMS
You have to get the liberty pass from a pokemon event. You can also catch Victini at liberty island.
fullmoon island,ison island,noomoon island