Yep and well Original Boss made the GPD to 0 Achievements unlocked was because people were complaining that it would unlock the achievements that he already had thus they couldn't unlock them they're selves. I am trying to find others with more mods that they have turned on with the Dev Menu and see if any more mods will stick but sadly no one has uploaded there GPD
Well i have just started this game and i use the GPD and my achievements dont go away and i still can earn them im sure if you can unlock an achievement your gamerscore will re appear i dont think it does sync with xbl because you think about it if you mod your gamerscore and you sync it with xbl people say you can not get it to go back to 0 now your saying this does that ? it may look like that but i doubt it actually stays like it all i can say is mine is fine not sure why others are having a problem