If I use Hoopa's "Assault Gate" attack after I move it up to replace a Pokemon that was KO'd by an opponent's attack, does it do anything?
No, Hoopa was moved to the Active Spot during the opponent's turn, not during "this turn".
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
If I use Steenee's "Captivate" attack while Spikemuth stadium is in play, does the opponent put any damage counters on their Pokemon?
No, Captivate would not trigger Spikemuth since it was not moved during the opponent's turn.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
When using Carnivine's "Return" attack, do I have to draw until there are five cards in my hand, or may I stop with less than five?
You do not have to draw any cards, but if you choose to do so you must end up with exactly five cards in your hand; no more, no less.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
If my opponent has no benched Pokemon, does their Active Pokemon become Confused when I use Delcatty's "Captivating Tail" attack?
No. Confusion is only done to the "new Active Pokemon". If there is no switch, the Active Pokemon is not Confused.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
When using Centiscorch VMAX's "G-Max Centiferno" attack, can I get a Heat Energy from my discard pile?
No, you may not. Heat Energy only counts as a Fire Energy card while it is attached to a Pokemon, not when it is in the discard pile or anywhere else.
Source: TPCi Rules Team (2020-08-13)
When using Centiscorch VMAX's "G-Max Centiferno" attack, do I get +40 more damage for the Fire energy I attach during the attack?
No, the attachment of Fire Energy from the discard pile takes place after the damage calculation of the attack is done. Also, you don't get to attach the Fire Energy if the attack didn't do any damage.
Source: Darkness Ablaze FAQ (2020-07-31), TPCi Rules Team (2020-08-13)
If I have Eternatus VMAX with "Eternal Zone" Ability in play and my opponent uses Celebi's "Time Spiral" attack to devolve one of my benched Darkness type Pokemon to a non-Darkness type Pokemon with enough damage already on the devolved Pokemon to knock it out, is it KO'd before having to reduce my Bench down to 5 Pokemon, or if I discard it to reduce my bench is it not KO'd?
You would discard your Bench down to 5 first, then check for a KO. That means you could discard the newly devolved Pokemon to avoid a KO, even if Eternatus VMAX is the one being devolved!
Source: TPCi Rules Team (2020-08-13)
When using Diggersby's "Mining Rush" attack, can I discard cards one at a time or do I have to discard them all at once?
You may discard cards one by one for Mining Rush and stop any time before you reach the maximum amount specified in the attack. You do not have to declare up front how many cards you're going to discard.
Source: TPCi Rules Team (2020-05-07)
Am I allowed to use Gossifleur's "Call for Family" attack if my Bench is already full?
You can use the attack, but since it's public knowledge that you can't put any Pokemon onto your Bench the entire effect of the attack fails; you can't even search your deck.
Source: Supreme Victors FAQ (2009-08-27), PUI Rules Team (2009-08-27), PUI Rules Team (2020-05-07)