Easy, you can't, but you could migrate it from the older games.
Honey Trees
you cant that's a Pokemon move and Pokemon can learn it
U have 2 trade him
you have to trade him from Pokemon platnium
you have to find the man that deletes any move
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 can find Mewtwo in the Cerulean Cave.
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
Mewtwo is found in cerulean cave.
It's impossible to find Mewtwo in Platinum.
use your map to find out