You can catch him on Mt. Coronet (upper) B1F with the old rod.
mt coronet trust me
quiet cave on pokewalker
There is no 'platnium', but you can find it on wild pokemon.
You can't find Registeel in Pokemon Platnium. You just migrate it in Pokemon Ruby, Pokemon Sapphire, and Pokemon Emerald.
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you cant.
in girantinas cave
in the trophey garden
Honey Trees
No, you'll have to trade it from Platnium. Which in Platnium you find it in the Rock Peak Ruins.
you cant that's a Pokemon move and Pokemon can learn it
use your map to find out