You can't catch Celebi, but you can transfer it from Generation 4 into your game when you are able to use Poke Transfer. You can also trade.Celebi cannot be caught in the wild. You'll need to transfer it from the older Pokemon DS games into the Transfer Lab or trade for it from someone.
You would be able to trade Celebi to someone in order to get Genesect, Meloetta or Keldeo but you wouldn't be able to use an in-game Celebi in order to fnd Keldeo, Meloetta or Genesect in-game.
You do not get Celebi anywhere in HeartGold. The only ways you can get a Celebi is by downloading an available Nintendo event where it is offered however there wouldn't be anymore events for HeartGold or you can trade with someone else who was able to get a Celebi at an event.
You can Celebi by trading it over gts, or with a friend, you can use action replay to get Celebi, or you can get Celebi in an event.
Grass Pokemon
You are now able to battle the Pokemon in the snowpoint temple.
Celebi was able to be obtained in a special event, but you may also obtain it using an action replay
after the old mansion mission you will be able to play some missions clear some of them and you will get it
One can trade in Pokemon Yellow via link cable. Two Gameboy consoles can be connected via link cable and Pokemon can be traded across Pokemon Blue, Red, or Yellow.
Kyogre is not able to be caught in Ruby Version.
You can't the only way is to use gameshark and use the cheat and then you will be able to get a gs ball
Nothing, but if you trade the GameStop Jirachi, you get a new Pokewalker route. And currently, there is the "Yellow Forest" distribution via general WiFi. When you trade pikachu colored pichu to heartgold or soulsilver you are able to catch a rare Pokemon in a forest. I can not remember anything else. It's celebi.