Can i update my unloked iphone with an other iphones backup. What will happen?

So have an iPhone 4s that is unloked and is not updated to the ios7 recently I traded my other iPhone for a HTC at the store they transferred some stuff but not all and am thinking I can update the unlocked iPhone with the backup from the other phone that I have in iTunes I think I can do it but am afraid this is going to lock my phone. Thoes any body knows help please

The unlock has nothing to do with the software. You can update your iPhone.

You can but once you do that your phone will go back to its original software and not be jailbroken anymore