Can I use Sceptile's "Nurture and Heal" ability to attach a {G} Energy to a Pokemon that doesn't have any damage on it?
Yes, you can.
Source: Primal Clash FAQ (2015-02-05), TPCi Rules Team (2015-02-05)
The "Alpha Growth" Ancient Trait says "When you attach an Energy card from your hand to this Pokemon... you may attach 2 Energy cards." Does that mean I get to attach one additional Energy card or two additional Energy cards?
You only get to attach one additional Energy card, for a total of two cards attached at that time.
Source: Primal Clash FAQ (2015-02-05), TPCi Rules Team (2015-02-05)
Are Omega and Alpha effects considered Abilities? Will things that affect Abilities affect them too?
They are neither Attacks nor Abilities. They are something different called "Ancient Traits". Effects that apply to Attacks or Abilities don't apply to Ancient Traits.
Source: Primal Clash FAQ (2015-02-05), TPCi Rules Team (2015-02-05)
What happens if M Gengar EX uses its "Phantom Gate" attack to copy Xerneas EX's "X Blast" attack? Can it use "Phantom Gate" again the following turn at all or not? Or would it just not be able to copy "X Blast" twice in a row?
The X Blast attack puts an effect on Gengar that prohibits using that particular attack next turn. But M Gengar EX is using its Phantom Gate attack on the following turn, so yes it is able to copy X Blast twice in a row.
Source: TPCi Rules Team (2015-01-22)
If my opponent KO's my Active "Robo Substitute", would I get the extra benefits from Terrakion's "Retaliate" Attack or Toxicroak's "Revenge" Attack?
Yes, you would. Even though Robo Substitute does not give up a prize card, it still counts as a KO'd Pokemon.
Source: TPCi Rules Team (2014-12-04)
What happens if Kecleon with "Color Change" and Wobbuffet with "Bide Barricade" end up as Active Pokemon opposite each other? Does Kecleon change to Psychic, or does Wobbuffet shut off its power and Kecleon stays Colorless?
If Kecleon starts out as Psychic and then Wobbuffet becomes Active, Kecleon stays Psychic. But if Wobbuffet is Active first, or if they both become Active at the same time (including as the starting Pokemon), then Kecleon stays Colorless.
Source: TPCi Rules Team (2014-12-04)
The wording of Jamming Net is now as follows, "The attacks of the Pokémon this card is attached to do 20 less damage to each of the opponent's Pokémon (before applying Weakness and Resistance). (Don't apply Weakness and Resistance for Benched Pokémon.)" This tool should only impact the Pokémon belonging to the opponent of the attacking Pokémon.
Source: TPCi Announcement (2014-11-18), TPCi Rules Team (2014-11-20)
The wording of Fighting Stadium is now as follows, "The attacks of each {F} Pokémon in play (both yours and your opponent's) do 20 more damage to the opponent's Active Pokémon if it is a Pokémon-EX (before applying Weakness and Resistance)." This stadium should only impact the Active Pokémon-EX belonging to the opponent of the attacking Pokémon.
Source: TPCi Announcement (2014-11-18), TPCi Rules Team (2014-11-20)
When Dimension Valley is in play, if Mew EX uses its "Versatile" Ability to copy an attack from another Psychic Pokemon, will the attack's Energy cost be reduced by (CC)?
No. When Versatile copies the attack it uses the original attack cost regardless of the opponent's Pokemon's type, and then Dimension Valley reduces the cost by (C) since Mew EX is Psychic.
Source: TPCi Rules Team (2014-11-20)
If my opponent has Togekiss with the "Bright Veil" ability Active, does that prevent me from attaching Pokemon Tool F cards like Jamming Net or Head Ringer to their Pokemon?
No, Bright Veil does not prevent you from attaching the Pokemon Tool F card to your opponent.
Source: TPCi Rules Team (2014-11-20)