iPad: Using iTunes to restore causes automatic sync? I had a iPad mini(miniA) several months ago, and I got a new iPad mini(miniB) recently. On miniB's first run, when I was asked whether to set it up as a new device or restore from a backup, I chose to restore from miniA's backup and have iTunes to do the restore. Some days later, I find a problem: When I assign miniB to use a different FaceTime email address, miniA's original FaceTime email address gets lost and be automatically set to miniB's! Also, changes to miniB will be sync-ed to miniA -- quite unexpected. 

Is there any Apple official document describing this restore-and-sync behavior.

Yes, I really want miniA and miniB to use different FaceTime email addresses -- and I know of course they can, because my iPhone is using a different FaceTime email address than that on miniA . And the worst way I can imagine is factory reset my miniB then set it up as a new device. I'd like to know, is there other solution without wiping off miniB?

BTW: miniA, miniB and my iPhone all use the same Apple ID to access FaceTime service.
I think the only way you could do this is if, after you've synced all you want to miniB, change the iCloud account associated with the device (Settings > iCloud > Account > Enter new account info).

I have not tried this, but just at quick glance, I'm thinking it may work. Please let me know your results! If that doesn't work, we can try something else.