Is Floette's "Flower Veil" Ability stackable, such that if you have more than one in play it adds +20 for each "Flower Veil"?
Yes, that is correct.
Source: Flashfire FAQ (2014-05-08), TPCi Rules Team (2014-05-08)
Can I use Goodra's "Gooey Regeneration" Ability to discard attached Energy cards if there is no damage on Goodra.
Yes, you can.
Source: Flashfire FAQ (2014-05-08), TPCi Rules Team (2014-05-08)
Servine uses the attack "Wring Out" and flips heads against a Virizion EX with a single Grass Energy attached. It deals 30 damage, and the Grass Energy is discarded. Can the paralysis Special Condition be applied?
The Paralysis condition occurs within the attack text before discarding the energy. Since Virizion EX's Verdant Wind ability is still active the Paralysis is prevented, and then the energy is discarded.
Source: TPCi Rules Team (2014-01-02), TPCi Rules Team (2014-05-08)
If I use Aegislash's "Stance Change" Ability, to switch for another Aegislash, can I then use the new Aegislash's "Stance Change" if I want to?
No, even though you have switched to a new Aegislash card you cannot use Stance Change again because the effect of using it remains on that Pokemon.
Source: XY FAQ (2014-02-06), TPCi Rules Team (2014-02-06)
When using Aegislash's "Stance Change" Ability, do I have to switch the Doublade & Honedge underneath it too?
No, you only switch one Aegislash card for another Aegislash card.
Source: XY FAQ (2014-02-06), TPCi Rules Team (2014-02-06)
When using Aegislash's "Stance Change" Ability, what do I do with the card after I switch it with an Aegislash from my hand?
The Aegislash that was in play goes into your hand.
Source: XY FAQ (2014-02-06), TPCi Rules Team (2014-02-06)
If I use Inkay's "Upside-Down Evolution" Ability, does it remain Confused after evolving?
No, it does not. The phrase "this counts as evolving this Pokemon" refers to evolution rules that remove Special Conditions on that Pokemon.
Source: XY FAQ (2014-02-06), TPCi Rules Team (2014-02-06)
If Sigilyph with the "Toolbox" Ability has Plasma Badge and Reversal Trigger attached, do I get to search my deck for a card when it is KO'd by an attack?
Yes, you can. The tools are still present on the Pokemon when it's KO'd (assuming the attack does not discard the tools first), so you would get to use the effect of Reversal Trigger since Plasma Badge makes Sigilyph a Plasma Pokemon.
Source: TPCi Rules Team (2013-08-15)
Can you attach more than one tool of the same name to Sigilyph with the "Toolbox" Ability? And if so, do the effects of the tools stack?
Yes to both questions.
Source: TPCi Rules Team (2013-08-15)