Without an event or cheating device, Deoxys is simply out of the question. It's onobtainable. Ho-oh and Lugia cannot be caught in Fire Red either without an event, however they can be caught in other games. In Pokemon Coluseum, if you purify all 48 Pokemon and beat Mt. Battle in Battle Mode, Ho-oh will join your party. Then you must trade it to Fire Red. As for Lugia, it is caught as a Shadow Pokemon in Pokemon XD. You must purify all other Pokemon and then you are able to purify Lugia. Then you can trade it to FR.