I once had to perform a hard reset on the Samsung GT-C3010.
The reason was the password for SMS, which the owner of the phone forgot.
To make a complete reset to Samsung C3010, you need to dial *2767*3855# on your phone’s keyboard and wait until the phone restarts.
After a complete reset, all user data, contacts, including the password for SMS, SMS, etc., are deleted.
The settings are reset to the factory.