I have an existing app that's already released to the public which has a "single app" game center entry with many achievements.
Now i'm adding a new app with which I want the original app to share achievements. So there's a "Move to Group" button in my original app where I can transfer my achievements to a new Group. This process requires me to change the achievement ids to prepend "grp." to them.
If I do this, will it screw up the people who already have the old version installed? Or will the versions of the app that are already released will keep the original achievement ids?