1. The type of data to be protected depends upon your application. You can enable protection for any type of data 1. System startup code; 2. System startup (backup) code; 3. Calibration data; 4. User data) depending upon your requirement.
2. You can use any of the protection methods in your application.
3. I am not clear about your third question. Please clarify.
To help you better with this query, we would like to know more details about your application. Could you please explain your requirement in detail?
Thanks and Regards,