Compilation of all Legendary Pokemon locations & detailed guide in Pokémon Emerald

Timeline:
00:00 Rayquaza
02:47 Kyogre
06:16 Groudon
08:14 Latios/Latias
10:41 Regi Trio Unlock Preparation: Relicanth
12:00 Regi Trio Unlock Preparation: Wailmer
13:20 Regi Trio Unlock Preparation: TM28 "Dig"
13:52 Regi Trio Unlock
16:35 Regice
18:31 Regirock
20:10 Registeel

For unlocking Regi Trio,
1. Prepare Relicanth, Wailord(evolved from lv.40 of Wailmer) and a Pokemon learned with "Dig" in your party
2. Go to Pacifidlog Town, go West to find the spot and use Dive
3. Find the wall with text, read it and use Dive to arrive Sealed Chamber
4. Read the text on the wall at the back and use Dig
5. In next room, put Wailord and Relicanth in the first slot and last slot of your party respectively, and read the text on the wall at the back
6. The doors of Regi Trio's cave are unlocked

For Regice's puzzle, walk along the perimeter of the room clockwise
For Regirock's puzzle, use Flash in the center of the room
For Registeel's puzzle, use Rock Smash at two steps left and two steps down of the wall with text

Thanks for watching and I hope you enjoy!!