Yes, as long as it doesn't put him in check.
The objective of chess is to checkmate the king, where the king is in check by a piece and it cannot block the check, move to another square, or capture the piece checking the king.
The King is not allowed to be in check. If a piece is on a square where if the King were there, the King would in check, the King isn't allowed to capture it.
Yes, the king may capture the piece that is checking it.Yes, but only if that piece is on a square adjoining him, as a king has mobility of only one square per move.
The king can take another piece anytime, but it is not smart to do so until perhaps the last moves of the game, if at all.
Yes.
Yes, it can, as long as it doesn't put the king in check. PS, it's "capture", not "kill".
Only in certain circumstances such as having your king in check with no squares to move to and the only way to stop the check is to capture the piece delivering the check.
You cannot capture opposite king in chess. You can attack him with check, and your opponent should immediately defend it. If the opponent has no way to defend, it is checkmate and you are awarded victory of the game.
Yes. The only way is to move a piece so that it blocks your king from check and checks or attacks another piece of the opponent. Another way is for the king itself to attack the piece that is attacking it. Example is if the queen foolishly moves adjacent to the king without being protected by another piece, the king may capture the queen. It is not limited to simply moving out of check.
No. In addition to moving the King, check can be escaped by capturing the checking piece or blocking its path. Of course a Knight cannot be blocked, so that option is not available in that case. Also note that the King cannot avoid check by "castling".
The king can move one square in any direction. If it moves into a square that is occupied by another piece, it takes that piece only if the king is not endangered if it gets next to it in order to capture it.