The cheat above sounds like total bs
Go to the cave maniac's cave - and in that cave there will be Hippopotas - so catch one of those
Then you go to the secret island ( you must cyndquil and rayquaza and groundon and hycolma wich is a pokemon that is only in pokemon platinum and you must have beat the elite four then go to the town with the trees and use dig then use hidden power the island will show up on your map blinking. Then put all the unowns in your 1 2 3 4 5 6 spots then go to the big rock and use hidden power by the unown and then a big cave will open go inside and there will be 20 chests but it says to open 21 so there is one hidden next to number 16 it is in front of it you have to use your item finder then in 12 of them there is master balls and then in 8 of them there are any stones that you want all you have to do is go to the computer next to the house near the cave and have the stone type that you want in front like charizard will give you a fire stone. You can also catch hidden pokemon that people say you can't catch.
If you catch a-z then the cave above will have ! And ? And a rare candy and then go to this kid in a house near the caves and he'll give you stickers for the unown if its the first in the party
You go back to the cave in celestic town and arceus will apper but fist you must kill darkrai not catch but kill darkrai