unlock all other trophies in a game
trade it.
i don't think you can
the easiest way is to hack.
With a Budew.
All you have to do is use this link. The book club offer is the easiest and cheepest. http://www.YourPS34free.com/index.php?ref=5899833 GET YOUR FREE PS3!!!!!
battle and win them
Battle every trainer you see
In Pokemon Platinum the easiest way to get a Chansey is to find one on routes 209,210 or trophy garden ,you can also get a happiny egg by talking to the hiker near the south east exit of hearthome city,or the trophy garden ,then give happiny an oval stone [first floor of lost tower] or you can find it on wild happiny,chansey's ,make it hold it,then level it up one level
The easiest way is directly connected to a modem/router or router. You'll need a cross-over cable (included with your PS3), or can use the wireless function if your router supports it.
use hypnosis after taking its hp down
Easiest way is to play coin launcher wait till it shows up and shoot your coins at the trophy to get it, medium or hard way is to play the subspace emissary and open all the orange and green cubes to get the trophy.
Either cheat or "chain" 40 pokemon.