They're in Ever Grande City! To get that city, you need pokemon that can climb the waterfall. Before reach the Elite Four, you must have 8 badges and pass the Victory Road.
Elite 4 E4
NO
In Pokemon Emerald you cannot.
same as emerald go to sky pillar and get after elite 4 or before elite 4.
you must catch all Pokemon and defeat the elite 4.
after you beat the elite 4
Electrode
in elite 4.
lalala
A good team to beat the elite 4 is Pokemon in the levels 50-100.
Fire and water are the best combination to beat the elite 4.
you must have 70 lv Pokemon or higher