Recovering files from DMG

Double click the disk image and it will open like a hard drive. Copy the files from it onto your re-installed Mac, or you may be able to use migration assistant.

When you made the disk image, did you make it from the Macintosh HD - Data volume? If you made it from just plain Macintosh HD, you didn’t back up your data.

USB Installation & Wipe and Install

Caution - the below method will Wipe ALL Data and there is not recovery - period.

How to fix a split Fusion Drive - this only applies if a Fusion Drive is involved.

To perform this action will require booting from a Bootable Installer. 

This will have to be performed from a Qualifying Computer to run the version of macOS to be made on the Bootable Installer. Example : Bootable Installer of Monterey would have to be done on a computer that Qualifies to run Monterey

Once that is done read on for preparing the Destination computer 

>> Only works on Intel Based Apple Computers. <<

Extra Special Notation regarding the Touch ID equipped Apple Computer.

About Startup Security Utility and Must Enable from Recovery Mode the ability to boot from External Drive Before Attempting 

1 - Shutdown computer and disconnect all external drive Except the newly created Bootable Installer.

2- Restart and immediately hold the OPTION key until the Startup Manager appears and choose the USB Drive. 

3 - It will present options >> Disk Utilities >> View >> View ALL attached Drives. 

4 - Choose the Upper Most Drive ( not the volumes indented and list below ).

5 - The drive normally is called Apple Media or Apple SSD - that is the drive to Erase and format as APFS with the GUID Partition Map.

6 - Once that is done >> backup out of Disk Utilities and choose install macOS. 

7 - Follow the prompts and it may automatically reboot several time. 

8 - Upon a final reboot - Setup Assist will present with the newer version of macOS.

That doesn’t sound good