Can I choose to move less than 4 damage counters on one or more of my Pokemon when using Drifblim's "Damage Transport" Attack? Or can I choose to skip any of my Pokemon?
No, if you have 4 or fewer damage counters on any of your Pokemon you must move them.
Source: Ultra Prism FAQ (2018-01-19), TPCi Rules Team (2018-02-01)
What happens during Drifblim's "Damage Transport" Attack if I have less than 4 damage counters on one or more of my Pokemon?
If there are 4 or less damage counters on one of your Pokemon you must move all of them.
Source: Ultra Prism FAQ (2018-01-19), TPCi Rules Team (2018-02-01)
If my opponent has no benched Pokemon, does the current Active Pokemon become poisoned if I attack with Roserade's "Inviting Poison"?
No, it does not become poisoned. If there's no switch to the bench there's no "new Active Pokemon" to become poisoned.
Source: Ultra Prism FAQ (2018-01-19), TPCi Rules Team (2018-02-01)
After time is called at the end of a match, what happens if I use Dialga GX's "Timeless GX" attack during the "plus three turns" part?
If you use Timeless GX when time is called during your turn, you would then get "Turn 1" instead of your opponent. Likewise, if you use it during Turn 1 you would also get Turn 2 and your opponent would get Turn 3, and so on... However, if you use it on the final turn of the match you do not get an extra turn.
Source: Ultra Prism FAQ (2018-01-19), TPCi Rules Team (2018-02-01)
When you use Dialga GX's "Timeless GX" attack does Poison still happen in between turns?
Nope, the attack says to "skip the between-turns step", so Asleep, Poisoned, Burned, and any other between turn effects also get skipped."
Source: Ultra Prism FAQ (2018-01-19), TPCi Rules Team (2018-02-01)
If I use Arceus' "Type Switch" attack and choose a type, what happens if I use Ninja Boy to switch Arceus for a Basic Pokemon of a different type? Does the new Pokemon become both types or does the new type supersede the choice from "Type Switch"? Or what if you Ninja Boy for a dual-type Pokemon like Volcanion EX that is Fire/Water?
The type chosen by Type Switch overrides the Pokemon's actual type, so the new Pokemon would become the type chosen rather than its regular type. And in the case of a dual-type Pokemon it would become the single type that you chose for Type Switch.
Source: TPCi Rules Team (2017-12-21)
If your opponent used Sandshrew's "Sand Attack" on the previous turn, and you attack with Passimian's "Intentional Grounding" which requires you to discard a Tool from your hand or the attack does nothing, do you discard the Tool before you flip for the Sand Attack effect or after?
Flip for the Sand Attack effect first; if it's tails your attack ends immediately, or if it's heads you proceed with your attack as normal.
Source: TPCi Rules Team (2017-12-14)
If I use Xurkitree GX's "Lighting GX" attack to put a card from my opponent's hand face-down as one of their prize cards, should we mix up the prizes so he doesn't know which one it is or does it stay wherever I put it?
Rearranging the prize cards is not part of the attack, so wherever you put the new prize card is where it should stay until some other action causes the prize cards to be rearranged.
Source: TPCi Rules Team (2017-12-07)
If my opponent uses Sudowoodo's "Watch and Learn" attack to copy the attack my Pokemon used last turn, what would happen if I use my own Sudowoodo's "Watch and Learn" attack on my following turn?
Your Sudowoodo would copy your opponent's Watch and Learn attack, not the attack your opponent copied. So unfortunately your Watch and Learn would do nothing.
Source: TPCi Rules Team (2017-12-07)
Zoroark GX's "Trickster GX" attack allows you to copy an attack from any of your opponent's Pokemon. Does this allow you to copy an opponent's GX attack or not? If so, what if your opponent has already used up their GX attack for the game?
Yes, Trickster GX can copy an opponent's GX attack, even if the opponent has already used up their GX attack for the game. It does not count as using 2 GX attacks.
Source: TPCi Rules Team (2017-12-07)