If Ariados' "Leech Life" attack does 30 damage but the opponent's Active Pokemon has only 10 HP remaining, how many damage counters will be removed from Ariados?
Leech Life does 30 damage, which is not affected by the fact that the KO only required 10 damage. Therefore, Ariados will remove 3 damage counters, or all if there are less than 3.
Source: HeartGold & SoulSilver FAQ (2010-02-11), PUI Rules Team (2010-02-11)
If the Defending Pokemon is currently protected from effects of attacks, do I apply Resistance to Donphan's "Rock Hurl" attack or not?
No, because the phrase "Don't apply Resistance" is part of the damage calculation, not an effect of the attack.
Source: HeartGold & SoulSilver FAQ (2010-02-11), PUI Rules Team (2010-02-11)
If the Defending Pokemon doesn't have any Energy cards attached to it, does Typhlosion's "Flare Destroy" attack still require Typhlosion to discard an Energy from itself?
Yes, if the attacking Pokemon has any Energy cards attached, it must discard one of them.
Source: HeartGold & SoulSilver FAQ (2010-02-11), PUI Rules Team (2010-02-11)
Can I use Jynx's "Mimic" attack to draw cards from my deck when I don't have any cards in my hand?
Yes, but you must shuffle your deck first before you draw.
Source: HeartGold & SoulSilver FAQ (2010-02-11), PUI Rules Team (2010-02-11)
When I use Typhlosion's "Flare Destroy" attack, which player chooses the Energy card to discard from the Defending Pokemon?
The player that used the attack gets to choose which Energy cards get discarded from both the Active and Defending Pokemon.
Source: HeartGold & SoulSilver FAQ (2010-02-11), PUI Rules Team (2010-02-11)
Can I use Jynx's "Mimic" attack to shuffle my hand into my deck when my opponent has no cards in his or her hand?
Yes, but you won't draw any cards after you shuffle it in.
Source: HeartGold & SoulSilver FAQ (2010-02-11), PUI Rules Team (2010-02-11)
If my opponent uses Pichu's "Playground" attack on the first turn of the game, and I am going second, can I evolve the Pokemon I put onto my Bench with "Playground" since I did not put them in play on my turn?
It is a basic game rule that neither player can normally evolve any Pokemon on their first turn of the game, even if they are going second.
Source: PUI Rules Team (2010-02-04)
May I use Ambipom [G]'s "Tail Code" attack if my opponent only has an Active Pokemon and no Benched Pokemon?
Yes you can, although it won't move or discard the energy. There must be a Pokemon on the bench or you can't move the energy off the defending Pokemon.
Source: PUI Rules Team (2010-01-28)
If I use Ambipom [G]'s "Tail Code" attack to move an energy card from the Defending Pokemon to one of my opponent's Pokemon that has an Unown-G attached to it, what happens?
While Unown-G prevents the attachment of the energy to the protected Pokemon, it does not prevent the removal of the energy card from the Defending Pokemon. The energy card is discarded.
Source: PUI Rules Team (2010-01-14)
If the Defending Pokemon is Knocked Out by Dialga-G Lv.X's "Remove Lost" attack, is a coin still flipped to see if the Energy attached to the Defending Pokemon will be sent to the Lost Zone?
Yes, you calculate the damage dealt first, then flip for the energies to go to the Lost Zone, and finally remove any Pokemon that are knocked out.
Source: PUI Rules Team (2009-04-02)