Time Machine

[anpaman]

Hi all

Does time machine also back up Mac OS ? So I able to reisntall it from time machine.

My MacBook Pro 2017 currently use High Sierra if I upgrade to Mojave and it got error could it still reinstall High Sierra ?

Thank

 

[MacCheetah3]

Apparently, it's doable. However, I'd be prepared to do a proper reinstall and restore from backup just in case.

Option 2:

3 Ways to Downgrade to an Older Version of macOS

Want to downgrade your Mac to a previous version of macOS? Here are several ways to revert macOS versions if you’re not happy.

www.makeuseof.com

An old walkthrough:

How to downgrade Mac OS X with Time Machine

If you have a Time Machine backup, reverting is a much quicker process.

www.cnet.com

 

[appltech]

An old walkthrough:

How to downgrade Mac OS X with Time Machine

If you have a Time Machine backup, reverting is a much quicker process.

www.cnet.com

Where did you find that one? It's a bit archaic

Anyway, yes, the first guide explains what to do to downgrade using Time Machine. Just make sure to select the correct backup when doing that (steps 5 and 6 in that guide).
Downgrading with Time Machine must be the most painless way of doing that.