How to get all (Or most) Legendary Pokemon in Pokemon Emerald

I'm trying to go through Victory Road and need a Legendary Pokemon to help me, I need at least one Legendary Pokemon so if I can get some help on trying catch one of them, please let me know how. Thanks!

You cannot obtain every single legendary (including Deoxys, Mew, Mewtwo, etc) without cheat codes or Action Replay. However there is one glitch (with no need for Action Replay or Gameshark) where you can hatch any Pokémon in the game called Glitzer Popping/pomeg berry glitch. There is a video from PokeTips showing the whole process,

. For more in depth info visit https://bulbapedia.bulbagarden.net/wiki/Glitzer_Popping. Extra Info: This will only work on Pokemon Emerald Version and may be dangerous to your save file if you do not do the glitch properly. Also because you said that you’re gonna use the Pokémon to go through victory road, I assumed you are going to use the legendary Pokémon for the elite four battle, but to do the glitch you will have to beat the elite four and got into the hall of fame. You still can do the glitch as soon as you reach Fortree City but you will probably go through a lot of problems (mostly because you cannot clone before elite 4). Hope this helped.