HI nhurka, You can navigate to [about:accounts] to click on manage on a desktop or from an android device in Firefox you can go to Settings > Sync > and tap or untap on what to sync. I think it will stop it from both ways, all devices merge on sync at this time.

settings > Sync > If I click "manage", following screen appears: How exactly I can command to wipe out content of sync's server & upload there local back up?

Sync has always had a problem* of mangling and duplicating bookmarks. I suppose I am not surprised to see it still happens.

I have not got time at the moment to give full details but hope this still helps.

Sync is very much a double edged sword,

• It helps by seamlessly syncing bookmarks between devices, and now New Sync even lets you use it from a single device to the server.
• But new sync gives no options to control Sync direction. And clearly is still capable of messing up bookmarks in a manner that is difficult almost impossible to sort out other than to rely on the last good backup.

You can use the bookmarks checkbox to turn off the bookmark syncing but you need to sort the mess out manually. Rather late now to mention that it is always a good idea to periodically manually backup your bookmarks.

First of all backup the profiles on each device (That at least preserves information). If this has happened recently you can possibly restore to a previous bookmarks backup. Take care though to make manual backups of bookmarks as you work. Restores overwrite & destroy bookmarks. Note HTML backups can be appended, and the files and folders are easy to edit and read. There is also a possibility of the Windows OS having a copy of the database, (places.sqlite - a hidden, Firefox profile file) but again care with ensuring you have backups before replacing.

* Bug 812348 - Firefox Sync duplicating and scrambling bookmarks & folders

(Additional info not updated for Fx30, - based on Firefox 29 menu - but linked articles will be up to date) If you have any current bookmarks save them now as an HTML files by exporting them as HTML. This sort of backup has the advantage that it can be appended to current bookmarks.

• see Export Firefox bookmarks to an HTML file to back up or transfer bookmarks

It is important to note the ordinary backups overwrite and destroy any existing bookmarks when you import them.

• Do a full backup of bookmarks before you attempt any restore.
  See Restore bookmarks from backup or move them to another computer

The bookmarks themselves are stored within the Firefox profile and the file is called places.sqlite , that is the file you want. (There are also backup bookmarks within a backup folder inside the profile,they may also be useful files.)

• You can find the profile from
  Firefox Button -> Help-> Troubleshooting Information -> [Open folder]
  See Profiles - Where Firefox stores your bookmarks, passwords and other user data_how-do-i-find-my-profile
• This explains the Windows feature http://windows.microsoft.com/en-US/windows7/Previous-versions-of-files-frequently-asked-questions
  Previous versions are available from right click options. Just take care with overwriting files, always back them up first

"But new sync gives no options to control Sync direction." Is there way to revert to old sync? Should I install older version of firefox? If I should, which one?

"it is always a good idea to periodically manually backup your bookmarks" Done automatically by FEBE

It is not recommended to go back to the old version of Sync

The old version is being retired it will stop being available shortly, so you need to get used to using the new version.

IIRC it is actually possible to force the Old Sync to work with Fx29 & Fx30 by using an old profile or hacking the preferences, but I do not think I should encourage users to try that, although it would be better than using an old version of Firefox which is definitely bad. In fact using an old outdated version of Firefox is so bad it is usual to recommend using an alternative up to date browser from someone else instead.

Firefox ESR is intended for corporate users, it is secure, it will at present use the old Sync. That will update soon to use the New Sync though, and at that point I imagine the Old Sync will probably be fully deprecated i.e. not available at all.

It is possible to use the feedback System to leave a short comment about Sync. I would recommend doing so, but unless very many like minded persons make comments I doubt it will have any effect.

• Use https://input.mozilla.org/en-US/feedback
  • Interactive contents display available here https://input.mozilla.org/en-US/ eg Sync Comments

Great that you use FEBE You should be able to rollback to an older set of bookmarks with that.

"Use https://input.mozilla.org/en-US/feedback"

Done: https://input.mozilla.org/en-US/dashboard/response/4509310