Downgrading to earlier MacOS versions Answer

That’s not so much a downgrade as it is an erase-and-reinstall.

Starting over on some version of macOS supported by the particular Mac does usually work, yes.

Versions of macOS older than the first version supported by the Mac won’t work.

Restoring newer files to old gets trickier, if there is no backup from the older version.

Files (settings, preferences, etc) modified by macOS don’t tend to downgrade at all well.

Cross-version apps and tools (word processors, etc) tend to be less sensitive to macOS versions.

kshlok494 wrote:

There are some free internet storage systems, maybe you can use those.

If your used storage is too large, then you have to backup

Free storage isn’t the issue, it’s all the pesky files and settings that get modified during and after upgrade, changes that can’t easily be backed out or reversed on any downgrade. Downgrades are either manual, or they’re erase-and-install and maybe then manually copy over the version-independent files.

👍