Boros Strike-Captain

• WWizards of the Coast2024-02-02
  Official Ruling
  Once a battalion ability has triggered, it doesn't matter how many creatures are still attacking when that ability resolves.
• WWizards of the Coast2024-02-02
  Official Ruling
  Similarly, once you attack with three or more creatures in a single turn, you can still play the exiled card that turn no matter what happens to those creatures.
• WWizards of the Coast2024-02-02
  Official Ruling
  If Boros Strike-Captain leaves the battlefield, the effect allowing you to play the exiled card if you attacked with three or more creatures continues to apply, even during later turns, as long as you attack with three or more creatures during those later turns.
• WWizards of the Coast2024-02-02
  Official Ruling
  The three attacking creatures don't have to be attacking the same player, planeswalker, or battle.
• WWizards of the Coast2024-02-02
  Official Ruling
  You pay all costs and follow all normal timing rules for a card played this way. For example, if the exiled card is a land card, you may play it only during your main phase while the stack is empty.

Rulings via Scryfall