The Chess: A Clash of Kings is a puzzle game using chess pieces rather than a game of chess: across 24 levels you have to reach the Red King's square, sometimes by sliding halves of the board or using gravity-switching squares.
You don't need to know chess to play — clicking a piece shows every square it can reach — which makes it a genuinely good way to learn how the pieces move.
No — clicking a piece highlights every square it can reach, which makes the game a good introduction to how the pieces move.
Twenty-four, with sliding board halves and gravity-switching squares adding mechanics beyond standard piece movement.
No — you can take as long as you like, and walkthrough videos are available from the main menu.