When you check your opponents king before they castle, can they castle after the check, or can the king only move one square to move out of check?
You can check them on any move.
They can't castle while they are in check or to get out of check but if they get out of check without moving their king or rook, they can castle on a later move.
A king only moves one square at a time except when castling.
When you check your opponents king before they castle, can they castle after the check, or can the king only move one square to move out of check?