LR sync creating many duplicate collections after restoring a backup catalog

1. You may find that your original Collections are no longer synced and the new one's in the "From Lightroom" collection set are the ones that are synced.   
2. You may also find that the synced ones under "From Lightroom" contain SP's (Smart Previews) for the images that had been imported into LrC and synced to the cloud.  These SP's should be up to date except for Keywords and they will be missing all the LrC edit history.   
3. The images in your original collections will have all their edit history but, as I said are probably no longer synced. 
4.  Where the new duplicates are SP's from the cloud, they will be in a folder (I think it's called something like 'previews-from-lightroom') which is a subfolder under whatever folder you have set in preferences as the desitination for images downloaded form Lr/Cloud.  These SP's will not have physical image files on disk, but that subfolder will be created on disk.
5.   In the case where Lr./Cloud had full size original images, you now have two copies of those images in LrC and on Disk.  The new ones from Lr/Cloud will be in the folder specified in preferences for Lightroom downloads. 

If all of the above is the case, AND you don't mind having SP's (Smart Previews) in the cloud in place of any full size originals you may have had there before,  then here's how I'd get back to normal.  If you want to keep full size originals in the cloud it's more complicated so don't follow these steps if that's the case.

1.   Verify that all the new collections have original collections with the same images (the original collections will point to images in their correct folder locations, the new duplicates will point to images in the designated Lighroom download folder)
2.   Un-sync ALL those new collections under "From Lightroom"  - DO NOT SKIP THIS STEP
3.    For each now unsynced duplicate collection select all the images, right click on one and click on "go to collection".  Assure that they are not in any of your original collections. 
4.    With them still selected go to the "All Synced Photographs"  special collecton and remove them.
5.    Go back to the un-synced duplicate collection and "remove" all the ones that are SP's and delete the ones that are full size originals after assuring that you have the same images in one of your regular folders as well.
6.    Now re-sync your original collection.

That should get you back where you were.  However, also be aware that changes you made in either Lr or LrC after you had created the backup you restored may have special issues - especially if you had deleted or removed images from either Lr or LrC afte the backup was created that now came back to LrC with the restore.  Some of these will never-ever synce again.  These will casue mismathes where the image is now present in LrC but is not in the cloud and can't be synced with the cloud.   It's way too complicated for a forum post (I'm working on a blog article on this very topic but still have some work to do on it).  When done it will be posted in www.danhartfordphoto.com under the "Artcles and Blogs" menu.