I heard that if you beat the E4 five times in ORAS, you will have a chance to pick either Xerneas or Yveltal. Is this true? //(Right now, I'm almost done with beating E4 the fourth time, so I can save my butt from training >.<')\
Xerneas and Yvetal can only be obtained in ORAS by transfering from X/Y
Beating the E4 a 2nd Time will get you a Metagrossite but no ther rewards after the 2nd.
Nope. This isn't true. It is only possible to get one legend per game, and they're version exclusive for XY only
You only receive Xerneas and Yveltal by trading.