You can either leave 2 pokemon (Male and female, female with Ditto, male with Ditto) In the Daycare Center, or talk to the man near the East exit in Hearthome City. Hope this helps!
from Pokemon FireRed
No.
There is no 'platnium', but you can find it on wild pokemon.
You can't catch a Charmander in Pokemon Platnium, but someone can trade you a Charmander egg or a Charmander and you may evolve it to Charmeleon then Charizard.
Mew can't lay an egg.
You can't find Registeel in Pokemon Platnium. You just migrate it in Pokemon Ruby, Pokemon Sapphire, and Pokemon Emerald.
== == == ==
No way. It didn't exist in that generation.
Honey Trees
in the trophey garden
in girantinas cave
No, you'll have to trade it from Platnium. Which in Platnium you find it in the Rock Peak Ruins.