Deoxys, Latios, Latias, Rayquaza, Groudon, Kyogre, Regice, Registeel, Regirock, Mew, Ho-oh, Lugia
all the legendaries and how to get them here http://www.psypokes.com/emerald/legendaries.php
Use Gameshark.
its not an emerald its RAYQUAZA the main legendary Pokemon in Pokemon emerald.
You have to trade it from FireRed or LeafGreen
beat the Pokemon league in fire fed and emerald then trade them and if you want duplacat them.(duplacating only in emerald)
all i know is how to get the regis and latios or latias.
rayquaza
The three legendary Pokemon in Pokemon emerald is Kyorge, Groundon and Rayquazer.
Groudon, Kyogre, and Rayquaza. Groudon is the fire legendary pokemon, Kyogre is the water legendary pokemon, and Rayquaza is the air legendary pokemon.
Raquaza (sorry if I mispeled that)
No,but you can migrate your legends from firered leafgreen emerald ruby or sapphire
Rayquaza if you want the details go to serebi net and type in rayquaza