I use Hekasoft (any time I make a signficant change to any of my browsers' settings or data) to manually back up the relevant personal data/settings to an external hard drive.
Had to look this one up. Looks like a good program. I don't use Freefilesync as a "Syncing" backup for Opera, rather I just make a mirror backup of the 4 copies of Opera (Three of 56.xxx and one of 12.18). But with Opera's syncing capability I've never had to restore a version of 56.xxx or its predecessors. I have 12.18 (Used for email only) installed on my e: drive including the profile and when I need to "Restore" it I can just copy it or the backup to a new computer. Works great for me. I usually backup at least every other day.
The program does look interesting in that you can use it to backup all your browsers (I have IE, Edge, FF also).
Where Freefilesync shines for me is I keep everything important to me in d:\My Documents and I sync between my laptop and desktop. Works great.
On another note, I'm sending you a PM here with a weird Opera 12.18 problem.