For most "fixing" needs related to firmware or operating system failures, follow these standard steps: How To FIX iPhone Stuck On Software Update!
: Official parts are linked to the logic board to maintain security features like Face ID and Touch ID. Fix My iPhone 2.0.3
If you are looking for a guide to modern iPhone repair or a "paper" on official practices, the following sections outline current official protocols and historical context: 1. Modern Official Repair Protocols For most "fixing" needs related to firmware or
Apple now provides a Self Service Repair program for users to perform their own maintenance. Fix My iPhone 2.0.3