Lots of variables, but you must remember that xbsall's P940 recovery app he he uses has recovery in system partition. The recovery you had before was probably in recovery partition. They write restores from two different places. Probably you would get an error, but not positive. Understanding that may take some Googling...
If you try it, back up before trying to restore the old backup. Then you could hopefully restore if the restore fails, know what I mean?
Probably the safest thing is to use the all in one tool to install recovery in recovery partition and use that one to restore backup.
I do know when I have restored backups, I have wiped Dalvik, Cache, and Factory Reset (in recovery) and then restore. Then it works. Some people wipe system too.
You can usually flash to recover from a problem, but then you have to set your phone up again