Hey guys, since ORAS has officially come out now, I might as well ask this.
As we all know you can't Mega Evolve two Pokémon in the same battle... however can you change Groudon/Kyogre into their Primal Form and Mega Evolve a Pokémon, such as Rayquaza in the same battle?
I'd probably say no, but there are a few reasons why I'm not sure about this, one being that you don't change Groudon and Kyogre's Form with a Mega Stone, but with the Red/Blue Orb. Also according to Showdown when given the Red/Blue Orb, Groudon and Kyogre revert into their Primal Form as soon as they enter the battle, I don't know how they actually know this, but it's what happens on Showdown.
Please DO NOT test this out on Showdown, I've already tested it on there and it allowed me to Mega Evolve Gengar and change Kyogre into it's Primal Form in the same battle. However, it also allowed me to change both Groudon and Kyogre into their Primal Forms in another battle, because of this I deemed Showdown unreliable, as let's be honest Showdown has made it's fair share of errors in the past.