Deoxys is not a Pokemon you will be able to capture in this game. As far as I know you could only get it in the GBA games through mystery gift. If you did happen to get that mystery gift, then you can transfer it through pal park.
You cheat or trade from a guy who cheated.
With an event you can get deoxsys here
I don't think you can but if you have Deoxsys on Pokemon fire red leaf green or ruby/sapphire emerald then you can transfer it to your Diamond
after beating league champion, compliting first pokedex (not jirachi and deoxsys) then random in woods.
you wait until the rocket launch is at exactly 50 then the guy will send you onto the moon
There is no rental Pokemon in in Pokemon platinum
You cant get Pokemon from Pokemon ranger to platinum!
how to get a togepi in Pokemon platinum
There is no grunt that you can give a Pokemon to in Pokemon platinum.
buy the Pokemon platinum book
yes there is a new Pokemon in Pokemon platinum. its name is Arcues.
The 151st Pokemon is Mew and is unobtainable in Pokemon Platinum.