How many Team Magma/Aqua Pokemon need to be in play in order to attack with Team Magma's Groudon EX or Team Aqua's Kyogre EX with the "Power Saver" ability?
Five. If there are only four or less, it can't attack. But keep in mind that it counts Team Pokemon on both sides of the play field, including itself.
If my opponent's Active Pokemon has the "Omega Barrier" Ancient Trait, can I use Lysandre to switch one of my benched Pokemon with it?
If your opponent's Benched Pokemon has "Omega Barrier", then Lysandre's effect will be blocked. But choosing a Benched Pokemon without "Omega Barrier" will cause it to switch with the Active Pokemon because the Benched Pokemon is the target of Lysandre.
If I attack using a Pokemon that has the "Omega Barrage" Ancient Trait, can I do things like attach an Energy or play a Trainer between attacks?
No, you would resolve all effects from the first attack and then either perform your second attack or pass. You don't get to go back into the main part of your turn again.
Source:
Primal Clash FAQ (2015-02-05), TPCi Rules Team (2015-02-05)
If I only have one energy card attached to Excadrill, can I use its "Omega Barrage" to attack with "Dredge" first to attach two energy cards, then attack a second time with "Mach Claw"?
Yes, that would work.
Source:
Primal Clash FAQ (2015-02-05), TPCi Rules Team (2015-02-05)
If I use Escape Rope but my opponent's Active Pokemon has the "Omega Barrier" Ancient Trait does he or she have to switch it? Or if they have a Pokemon with "Omega Barrier" on the bench can he or she choose that and not switch it to Active?
If your opponent has an Active Pokemon with "Omega Barrier", then Escape Rope's effect will be blocked. If a Pokemon with "Omega Barrier" is on the bench, choosing that Pokemon will not stop the effect as the Active was the target of Escape Rope.
Source:
Primal Clash FAQ (2015-02-05), TPCi Rules Team (2015-02-05)