Instructions
Insert the GameShark game disk into your PS1. Select the "Auto cheat mode" from the GameShark's main menu.
Select the "Final Fantasy VII" option in the auto cheat mode menu. You will then be prompted to insert your "Final Fantasy VII" disk into the PS1. Do so, then press the "X" button to continue.
Select the "Control Sephiroth" code in the Final Fantasy VII cheat list and press the "X" button. If the cheat is activated, this will deactivate the cheat.
Press the "Start" button to continue playing the game without the Sephiroth code.