TK_Come_On_Apple_Figure_It_Out Said:
"Can I go back to a previous macOS version?: Why must I invest in a new interface just for this lame update? This is terribly upsetting. I thought this update would be a good thing, now it's just a mistake. Can I go back to the old version? And can Apple please consider how frustrating this is? It's really not worth the update."
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Two Things:
It would be a matter of either (A.)restoring from a backup, or (B.)reinstalling the macOS anew.
A. Reinstalling the macOS:
Go Here: How to Reinstall macOS from macOS Recovery - Apple Support
Important: First, Back Up your Mac:
Create a Time Machine backup of your Mac, so that you can have something to restore your Mac from, should anything go wrong with the reinstall. Take this as a learning experience, knowing to always create a backup of your Mac, prior to making any major changes to it (i.e. update installation)
B. Reinstalling the macOS Anew:
See if this Site Helps: How to Reinstall the macOS Anew - No TMB Prior to Upgrade - User Tip. Format the hard drive with [the Previous Version], on step D.
In Depth:
Pretty much, it is a matter of:
- Erasing: and formatting your hard drive to APFS
- Installing: [The Previous Version] via a USB Bootable Installer
- Restoring: info from a Time Machine Backup, using Migration Assistan