While there are many versions of the Google Account Manager (GAM) APK available online, finding an official "v12" can be tricky because Google integrated many of these management functions directly into Google Play Services for newer Android versions. Where to find it

Authentication: Validating your login credentials for Gmail, Drive, and the Play Store.

If a device is reset via the recovery menu without removing the Google account first, the device locks on the initial setup screen. It demands the credentials of the previously synced Google account.

How to Safely Install (If Absolutely Necessary)

If you're an advanced user and understand the risks: