You can find Rayquaza in Sky pillar near from Pacific Log
After catching both Kyogre and Groundon, you come with them in your team and it'll be there. Beware, you have to trade with HG to get Groundon.
You cannot get it, you have to trade across with an older version or find someone willing to trade with you (cannot see on gts nego)
You can't find a Dawnstone in Pokemon Emerald
Go to You Tube and search for Munching Orange how to catch Riquaza!
go to the safari zone in emerald
If you mean he flew away from Sky Pillar, go to Sotopolis City and you should be able to go on from there. If you mean after he broke-up the fight between Kyogre and Groudon, go to Sky Pillar and catch him or just go over to the Sotopolis Gym.
he is the champion in emerald
You cannot find one in emerald (unless you trade or hack)
You cant find one in emerald BUT... you can trade from FireRed/LeafGreen
you can't get paras in emerald
where can i find groudan in Pokemon emerald
Sorry, you can't get Mantine in emerald