Gameplay » Special Conditions
In the rules it states that when a Pokémon evolves it becomes free of Poison, Sleep, Confusion, Paralysis, or anything else that may be the result of an attack. Does this mean that damage is also taken off of it when it evolves?
No.
Source: WotC Chat (2000-04-27)
Gameplay » Special Conditions
If an opponent already has Nidoking's Toxic double Poison, then next turn I use a "normal Poison" attack, does the opponent retain Toxic's double Poison condition or does it now become a single Poison condition?
It would gain a single Poison effect (the new effect replaces the old one).
Source: WotC Chat (2000-04-27)
Gameplay » Bench
Dark Dragonite's Pokémon Power does not have the "you cannot use this Power if your bench is already full" text like most other Bench-building powers and attacks do. Does this mean that by using Dark Dragonite you can bypass the normal five-Pokémon limit to your bench?
C'mon. That's silly. There isn't room to put the reminder text on every single card. The rule is the bench can only have 5 max (EVER).
Source: WotC Chat (2000-04-27)
Energy » Rainbow Energy
Can the First Movie promo Pikachu use Recharge to get a Rainbow Energy from the deck, or does it have to be a basic Lightning Energy card?
That would not work. Rainbow Energy only counts as all-basic energy types WHILE IN PLAY. This is not the case when it is in the deck.
Source: WotC Chat (2000-04-27)
Gameplay » Evolving/Devolving
Dark Pokémon evolve from Basic Pokémon. Once you evolve a Basic Pokémon into a Dark Stage 1 Pokémon, it CANNOT evolve into a non-Dark Stage 2 Pokémon, only a Dark Stage 2. "Once you walk down the Dark Path, forever will it dominate your destiny" - Yoda the non-Pokémon.
Source: WotC Chat (2000-04-13)
Energy » Rainbow Energy
Can you have more then 4 Rainbow Energy cards in a deck, since it changes into a basic Energy?
No, since it's not a basic Energy card you can only use 4 in a deck.
Source: WotC Chat (2000-04-13)
Gameplay » Discard Pile
Some players freely examine their own discard pile (or their opponent's) whenever they want. Is this allowed? Or can a discard pile only be examined when you have official business there (like after playing Item Finder).
Discard piles are open knowledge (either player could look through them).
Source: WotC Chat (2000-04-06)
Attacks » Smokescreen
If you use Smokescreen then retreat the Pokémon that is Smoke screened or if Magmar Retreats is it still in effect?
Smokescreen references the defending Pokémon, so if you bench that Pokémon the effect ends. If you bench Magmar then Smokescreen is in effect.
Source: WotC Chat (2000-04-06)