Use different pokemon. They should be at least level 50 the first time and level 70 the second.
Beat the Elite Four and the "Champion" (That's the most descriptive I can get to avoid spoilers)
Beat the elite 4 for the first time.
You can ONLY go to the Unova region without cheats and hacks. Although after you beat the Elite Four, new routes are unlocked with Pokemon from all of the other regions, though this is still in Unova.
The types for the elite four are as follows, 1.Dark 2.Psychic 3.Ghost 4.Fighting
In Ruby and Sapphire yes you need to beat the Elite Four first, but in Emerald you can catch Raquazza before or after you beat the Elite Four.
Yes. You must beat the Elite Four to get anywhere in Kanto.
you have to beat the champion
beat the elite four 900 times
After you beat the elite four you... Gotta Catch'em All! Gotta Catch'em All!
You need to beat the elite four before you can get Zekrom.
What to do after you've beaten the Elite Four? Well there's several things you can do! :3 First, you can always fill up your Unova and National pokedex completely, level up for pokemon, challenge rivals and friends daily in different areas of Unova, and even, beat the elite four again, and this time, challenge Alder! There's really a lot more to do after you're done. :3
No you can't use the azure flute after you beat the elite four