Just like any other pokemon, you battle with it. You can change its forms on the route East of Pewter City
You cannot find Deoxys in Pokemon HeartGold. Deoxys has to be traded from another game to get into HeartGold. The rocks to the east of Pewter City are used to change Deoxys' forms, but you have to transfer one using Pal Park, first.
You can't
You cannot find Deoxys in HeartGold, or SoulSilver. You can only get Deoxys through trading or at a Pokemon Event.
If you have action replay you can get any Pokemon you want. This feature works only in Pokemon Heartgold , Soulsilver and Platinum.
You cannot find a wild Deoxys in in Pokemon Soul Silver, or HeartGold. Deoxys can only be obtained by trading with someone or by getting one at special distributions.
Deoxys didn't exist when Pokemon Gold, Silver, and Crystal came out. If you meant HeartGold, then you'll need to migrate it or trade for it.
theres some how to get a deoxys in Pokemon heart gold but if you don't how use action re play
It is impossible to catch a Deoxys in the wild in HeartGold & SoulSilver. You need to get one at a Nintendo Event or transfer one from a GBA game. Theres a Deoxys mission in the 3rd Ranger game. Capture it and it will be comfortable in any 4th gen game.
It is completely impossible to get Deoxys in Pokemon Diamond, Pearl, Platinum, Heartgold or Soulsilver. Deoxys has not yet been distributed in any event and there is no hack into getting it. Furthermore, there is no way of getting a Deoxys in these games listed above.
First of all its called Deoxys and its only obtainable through Nintendo Events
No, Deoxys is only in Emerald, and you need to migrate it to can catch it. As for Celebi and Mew, you need a cheat code for them.
Unfortunatly, not -.-