Can I use Houndoom's "Single Strike Roar" Ability to search my deck for the special energy card Impact Energy?
No, you cannot. Single Strike Roar is only able to target a specific card named "Single Strike Energy". Although Impact Energy is a "Single Strike" Energy card, it is not "Single Strike Energy".
Source:
Chilling Reign FAQ; TPCi Rules Team (2021-06-17)
If I use Shadow Rider Calyrex VMAX's "Underworld Door" Ability, do I have to draw 2 cards?
Yes, it is not optional (it does not say "you may"). You must draw 2 cards if you are able to; you can only draw a single card if it's the last card in your deck.
Source:
Chilling Reign FAQ; TPCi Rules Team (2021-06-17)
Does Passimian's "Throwing Coach" Ability work if my Active Pokemon's attack doesn't do any damage to the opponent's Bench?
No, Throwing Coach only adds +30 more damage when you actually do damage to your opponent's Benched Pokemon. In other words, you have to do some bench damage in order to have "+30 more" done.
Source:
Chilling Reign FAQ; TPCi Rules Team (2021-06-17)
If Kecleon has no Energy attached and I attach a Psychic Energy to it when Old Cemetery is in play, will Kecleon's "Chromashift" Ability kick in before checking for Old Cemetery or will Kecleon get 2 damage counters?
Old Cemetery's effect will happen first, so Kecleon will receive 2 damage counters.
Source:
Chilling Reign FAQ; TPCi Rules Team (2021-06-17)
What happens if both Corviknight VMAX with "Lustrous Body" and Galarian Weezing with "Neutralizing Gas" are in play? Do they cancel each other out or what?
Lustrous Body takes precedence over Neutralizing Gas. It doesn't matter which one comes into play first.