just wandering?

I don't think you can I've tried but I couldn't get Celebi. I know you can get it on the crystal all hack.

The only ways to get Celebi in Crystal require either a cheat device (which isnt supported yet in RGR) or Pokemon cloning (which normally requires trading, also not yet supported).
Try the Celebi egg trick (click me) using the Storage system method (click me too) of cloning and see how you go. It might work.

dont understand the cheat

It's a very long and complicated cheat and there is no guarantee at all that it will work on anything but a real life gameboy.

Requirements for cheat:
One egg that will know Beat Up as its third move if it is hatched. An easy way to do this is on the Celebi egg trick page.
One bad clone. It's a cloned Pokemon a name made of only question marks (or, in some cases, blank),
its level will be 0 and its gender will be different to the original Pokemon that you cloned (eg. if the original was male the bad clone will be female).
Five other Pokemon that you dont care if you lose them
(because getting a bad clone might take some tries you will probally get some good clones you wont need, so there's the five right there).

To try and get the bad clone Pokemon make sure you have six Pokemon in your party and an empty box or two in the games Pokemon storage.
Save your game in front of the PC in game. Then go to the box, and deposit five Pokemon.
Exit the box, go to ''Change Box,'' select any box, and while it's saving, turn off the Gameboy.
Make sure that you do it while the message ''Saving, do not turn off the power'' is still there, otherwise it will not work.
Turn on the Gameboy and look at the box, the box should be the one that you deposited the Pokemon in.
You should have the Pokemon in your group and have the same Pokemon in the box.

Once you have the bad clone do the steps on the Celebi egg trick page at http://bulbapedia.bulbagarden.net/wiki/Celebi_egg_trick

almost postive you can. if does'nt work, then only for silver. go to cinabar island when it is dark and you have a super rod, lot of ultra balls, and powerful team of pokemon. there should be a small body of water on it(if not then seafoams because i forget which one it is). go to western side of water in the middle(this is important where you stand, don't be in the water on western side, be standing next to the body of water)and save it. if not night, you won't see it, and never will. you only see it once, even if you save first(this is just like the mew glitch in red, blue, yellow, and green)then put your super rod in the water and have fun catchin' lv. 120 celebi in the game(after fighting someone in your game excluding battles with connecter cord in trainer to trainer battles

P.S. if this doesn't work, then the same process at dark at heelix forest(if in heelix forest because i was confused, not sure of level of celebi

P.S.S. gold can't catch celebi