Spinerock Knoll

• WOTC Official Reminder Textofficial rules
  Hideaway — When this permanent enters the battlefield, look at the top N cards of your library. Exile one face down and put the rest on the bottom in any order.

• WWizards of the Coast2007-10-01
  Official Ruling
  It doesn't matter how the opponent was dealt damage or by whom, as long as the total damage is 7 or more. You don't specify an opponent when you activate the ability.
• WWizards of the Coast2007-10-01
  Official Ruling
  You'll get to play the card even if Spinerock Knoll wasn't on the battlefield at the time some or all of the 7 damage was dealt.
• WWizards of the Coast2007-10-01
  Official Ruling
  At the time the last ability resolves, you'll get to play the card if a player who is currently your opponent, or a player who was your opponent at the time they left the game, has been dealt 7 damage over the course of the turn.
• WWizards of the Coast2022-04-29
  Official Ruling
  Hideaway now causes you to put the rest of the cards on the bottom of your library in a random order instead of any order.
• WWizards of the Coast2022-04-29
  Official Ruling
  "Hideaway N" means "When this permanent enters the battlefield, look at the top N cards of your library. Exile one of them face down and put the rest on the bottom of your library in a random order. The exiled card gains 'The player who controls the permanent that exiled this card may look at this card in the exile zone.'"
• WWizards of the Coast2022-04-29
  Official Ruling
  Any player who has controlled a permanent with a hideaway ability since a card was exiled with it may look at that card.
• WWizards of the Coast2022-04-29
  Official Ruling
  Previously, permanents with hideaway entered the battlefield tapped. This ability has been removed from the definition of hideaway. Older cards have received errata to have an additional paragraph that reads "[This permanent] enters the battlefield tapped," and they now have hideaway 4.

Rulings via Scryfall