I've been having major issues with Mojave – slow-downs, connectivity issues, crashing – you name it. I tried to downgrade back to High Sierra.
High Sierra gets installed fresh, but my Time Machine backup was made on Mojave.
When I hit restore, all the sudden I have Mojave again. NO!
Is there a way to have my files back without MacOS automatically upgrading me back to Mojave?
Best Answer
You can only do a file restore, individual files/folders rather than a full disk restore.
Once Time Machine has been used on a newer OS, it will not allow you to go back.
Related - Revert to El Capitan
& also covered briefly in How can I download an older version of OS X/macOS?