I don't think you understand what does fully playable means. Fully playable means that you can get through the whole game without any problems. Anything that does not prevent the player from finishing the game does not count. Also, the game being playable or not has nothing to do with TC's question.The game itself is not 100% playable. At times the sound does not play at times, and it does not run very smoothly at all when boss battling or even monster battling. The problem however seems like it is coming from your side. You may not have registered the save file or corrupted the save file.
On topic: Did you set the correct save type? Have you try using other cheat codes to see if that happens as well?