What information about an opponent's deck and game state is public and can be asked about in a tournament?

Ruling: The number of cards in deck and cards in trash are public information that can be asked about. Rune numbers and information about cards in hand (including which card was added by effects or cards previously revealed) are private.

Nuances:

• Players cannot look again at an opponent's hand after effects like Mindsplitter or Sabotage have resolved
• Players can try to track hand information on their own, but opponents are free to shuffle their hand
• It is not public which specific card was added by effects like Stacked Deck