Yes.
You don't. Achievements are kept on a Valve database called the steam cloud. It is 99% impossible to un-achieve achievements.
You can only delete achievements that have "0" on their Gamerscore.
Delete the app and reinstall it
If the problem is because you uninstalled it by deleting some of the files, try to delete the driver via device manager and then reinstall it in a new folder, or delete the previous one and reinstall it there.
You can't, but you can delete all your Achievements and start over.
No, achievements very rarely get "deleted".
Sorry for such a short answer. No, you may not.
Delete your message or reinstall it in cydia hope it works.
Just format c: and if not delete c:\windows then u have to reinstall the OS , to make the system work
Uninstall and then reinstall the mouse driver. If after that you still have a problem, replace your mouse.
Sadly, you need to reinstall he game, or delete all of your creations and stars.
You delete it and reinstall it it's pretty easy