My setup I'm using Firefox 47.0 on Fedora (64-bit GNU/Linux) with GNOME shell, and on Windows 10 (64-bit).I also have Firefox Sync on an Android tablet, but I don't do as much web browsing on my tablet, so I haven't needed to look at the bookmarks there...I have been through all the tips offered on this site (unlinking, updating, re-linking...), with limited success : the history of the various devices in synchronized, but NOT the bookmarks.I tried to create a new account with a new email address, but I am still waiting to receive the email for verification (although the email address works fine).
In July, I first installed Sync on my PC (Windows 7), my smartphone and my tablet (both Android 4.2.2).
If not, sync will only sync data that is connected to the account and cannot be a reliable back up.
If you have a copy of the Firefox profile from before the reformat or a copy on another computer, Recovering important data from an old profile I am sorry that I could not be more helpful.
I'm worried about connecting my android device because if it will delete my old bookmarks I can't do anything to recovery it Hi!
You are absolutely correct in your caution around changing your password then adding a mobile device with bookmarks that have no back up.