Even if you do capture all the unowns, you still cant get a celebii. You just get 2 more unowns, a ? and a !
Not without cheating
I don't even think unknowns have anything to do with celebi
You can find celebi in the solaceon ruins. First go to the room where you get the four items, read the inscription, and battle 99 unknowns and the 100 battle will be celebi. WARNING: I don't know if this works because I never tried it but my friend did it and showed me the celebi and it came from the solaceon ruins.
I don't know for certain, but I believe there was an event for Celebi a while back. That was the only legitimate way to get Celebi in Platinum without trading it from another game. The only other way to get it is to use an action replay code (or gameshark). That's how I did it! XD
you can not catch celebi in Pokemon platinum
you cant
you cant get it
trade it from someone who did cheat that way you didn't cheat
When catching Celebi, you should have a cherish ball. Throw it and it will be an instant catch. (DO NOT USE A MASTER BALL OR ANY OTHER BALL.)
celebi is onlyobtainable throw Nintendo events
You can't, Celebi is obtainable by events. The only way you can find a Celebi in Pokemon Platinum is by cheating.
Actually you can get Celebi. First you need the National Pokedex then fly or walk to Solaceon Town and go to where all the unknowns are. Next you will need to defeat 100 unknowns. After doing that you have to go down to the place with the writing on the wall and where the 4 pokeballs are/were, and you have to read the wall writing 2 times. After that Celebi should show up. This might work better on Pearl or Platinum, not too accurate with Diamond. Well I hope I helped. Good Luck!