Korean Air???

Are there personal seatback screens on Korean Air Boeing 777 planes? I’m not talking about the 747’s, only the 777’s.
i mean are there any personal tv screens behind each seat for every passenger

Mostly, but not all routes. It depends on where you are going (or where you started from). You should call the airline desk and find out.
Korean Airlines 800-438-5000

Air France Safety Demo 747-400