Tangrowth's "Power Whip" attack should say, "This attack does 10 damage for each Energy from basic Energy cards attached to Tangrowth to that Pokemon."
Does Unown G's "GUARD" Poke-POWER prevent effects from attacks that the Unown G is attached to?
No, the Poke-POWER only prevent effects from an opponent's attacks, not your own. Unown-G's "GUARD" Poke-POWER should say, "As long as Unown G is attached to a Pokemon, prevent all effects of attacks, excluding damage, done to that Pokemon by your opponent's Pokemon".
Source:
PUI Rules Team (2008-02-21), Organized Play News (2008-02-28)
If I use Caterpie's "Pupate" Poke-POWER to successfully evolve into Metapod, can I then immediately use Metapod's "Emerge" Poke-POWER to attempt to evolve into Butterfree, all on the same turn?
If a Retreat Cost is set to zero by an effect, it cannot be increased. Note this is different than a Retreat Cost that was reduced to zero by subtraction.
Banette is receiving errata for its first attack, Ghost Head. Ghost Head can't cause Banette to Knock Out itself ... the attack has to leave Banette with at least 10 HP. "Put as many damage counters as you like on Banette. (You can't Knock Out Banette.) Put that many damage counters on the Defending Pokémon."
Electrode is receiving errata for the card to reflect that its Poké-Power can trigger when any attack Knocks Out Electrode, not just during its owner's turn. "If Electrode would be Knocked Out by damage from an attack, you may use this power. Electrode isn't discarded. Instead, attach it as an Energy card to 1 of your Pokémon. While attached, this card is a Special Energy card and provides every type of Energy but provides only 1 Energy at a time. (Has no effect other than providing Energy.)"
Source:
PUI Rules Team (2007-12-06), Organized Play News (2008-01-29)