Log in screen does not respond
 

I had to erase my iMac hard drive so used my Super Duper backup drive to erase and rebuild my internal hard drive. However, when booting on the now-reconstructed hard drive on the iMac, a different screen appears than the 3 user screen on the backup, which was the same as originally existed on the iMac before the problem.

Now, the login screen wants a name and password and none work. I cannot determine how to override it and get in and fix accounts in some way but don't understand why the backup isn't cloned to the internal drive and operate identically.

I've already replied to your emailed question, but this looks like you made a backup with "Copy newer" or "Copy different" rather than "Smart Update".