If one of my Pokemon was knocked out by an effect of an attack or an Ability, would I still be able to play Letter of Encouragement?
Yes, there is no restriction on how the Pokemon was Knocked Out. However, a KO during Pokemon Checkup such as from Poison or Burn would not count.
Source: Obsidian Flames FAQ; TPCi Rules Team (2023-08-10)
Do I include Brassius in the count of my hand?
No, by the time you are counting the cards in your hand Brassius is already in play; it is no longer in your hand.
Source: Obsidian Flames FAQ; TPCi Rules Team (2023-08-10)
If Pokemon League Headquarters is in play and I have Lunatone with the "New Moon" Ability and also Solrock in play, do my Basic Pokemon have an extra {C} cost to their Attacks?
No, but your opponent's Pokemon do.
Source: Obsidian Flames FAQ; TPCi Rules Team (2023-08-10)
What happens if I play Worker and cannot draw any cards? Do I still get to discard a Stadium or not?
Yes, they are two separate sentences so you do as much of it as you can.
Source: TPCi Rules Team (2023-07-13)
Say Gapejaw Bog stadium and Ting-Lu ex with "Cursed Land" Ability are both in play. If I put Lumineon V onto the Bench, can I use its "Luminous Sign" Ability or will it be blocked because it has damage counters on it?
Since Luminous Sign and Gapejaw Bog are simultaneous effects, it is up to the player to choose the order in which they will be applied.
Source: TPCi Rules Team (2023-07-13)
My opponent has Malamar with the "Contrary" Ability in the Active Spot. On my turn, I attach Blunder Policy to my Fuecoco and use its "Spacing Out" attack and I flip heads. The coin result will be treated as tails, but since the physical coin flipped heads do I get to draw 3 cards with the effect of Blunder Policy?
There is no distinction between the actual result of the coin flip vs. what the outcome is treated as. Regardless of what the physical coin shows the flip was tails, so you would get to draw 3 cards from the effect of Blunder Policy.
Source: TPCi Rules Team (2023-06-22)
Can you use Lost Vacuum to put a card into the Lost Zone if there is no Stadiums or Tools in play?
No, you cannot. Putting a card into the Lost Zone is a cost not the effect, and you cannot play Trainer cards for no effect.
Source: TPCi Rules Team (2023-06-01)
If I have a Honchkrow V with "Boss Pockets" Ability and 190 damage on it and three Emergency Jelly tool cards are attached, do all of the tool cards trigger at the same time or do they trigger sequentially?
They trigger in sequence, so the first Emergency Jelly would remove 120 damage and get discarded, but the second & third Emergency Jelly would not trigger since there is now more than 30 HP remaining and no more damage would be healed.
Source: TPCi Rules Team (2023-04-13)
If I have 6 cards in my hand and use Mimikyu's "Impersonation" attack to discard Erika's Hospitality from my hand, can I use the effect of Erika's Hospitality?
Since you have 5 cards in your hand after discarding the Erika's Hospitality you can use its effect.
Source: TPCi Rules Team (2023-04-06)