[keriah]

I have a MacBook Air (2017) that came with High Sierra installed. I would like to upgrade to Mojave (since it's the last OS that will run 32-bit apps) but would also like to be able to safely revert to High Sierra if I find something amiss with running Mojave.

I have read the thread "Downgrading from Mojave to High Sierra ... lessons learned" and would like to 'learn' what's relevant from it and also to not create my own sad lessons. So, before I begin, is there SuperDuper documentation I can study, and (also) are there specific states of my source and backup volumes that I should tend to before I begin?

My MBA has an SDD (2 partitions), with High Sierra installed on the 300gb partition, formatted APFS. (The other SDD partition is not bootable.) The backup is a SuperDuper-created copy (not image) to one 300gb partition, formatted Journaled HFS+, on an external 8gb USB drive.