Q&A for How to Find Latios in Pokémon Emerald

If you have a my boy free, split the codes in half. First two in one cheat, second two in another cheat. I would call the two cheats master and master2 for ease.

Tap the Menu Button, then tap Cheats, then Add Cheat. After that, enter a Cheat Name and Cheat Code.

You would need a GameShark to enter the codes. If you don't have a GameShark, then you can't enter the codes.

A few Pokemon, such as Kyogre or Groudon, can be encountered after obtaining Rayquaza. To encounter them, you will need to head to the weather institute, and talk to the scientist on the top floor, he will tell you about suspicious weather patterns over certain routes. If he mentions extreme sun, it will be Groudon, whose cave, the Terra Cave, will appear at a select location on that route, Meanwhile, on the other hand, if he mentions rain, it will actually be Kyogre. If you read the tips above, you can find Latias and Latios, depending on which you picked. Lastly, Mewtwo, The legendary birds, excluding Ho-oh and Lugia, and the legendary dogs, were obtainable through an event.

Latias and Latios are roaming Pokémon, which means they can appear on any route with long grass or surfable water. Try entering the cycling road and then coming back out to see if that helps.