http://www.serebii.net/platinum/nationaldex.shtml
Go there, and scroll down. There is a list of Pokemon for the pokedex, and their locations to see / catch them.
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
You get prinplup when piplup evolves. To get piplup you either pick chimchar, turtwig, or piplup.
you have to transfer it to the Pal Park after you get the National Pokedex.
The evolved form of Piplup is Prinplup. You get it by evolving Piplup at level 16.
beat every trainer
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.
== == == ==
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 need to find 210 Pokemon to complete the pokedex