Can I restore back up from Iphone 6 (iOS 8.0.2) to iPhone 6s plus (iOS9.1) using latest version of iTunes?

Hi all,

I faced a problem when I tried to restore back up from my iphone 6 to iphone 6s plus.

Currently my iphone 6 is iOS 8.0.2 and i want to restore the back up to a new iphone 6s plus with latest version iOS 9.1 and my iTunes on PC also updated.

Some of my applications in my old iPhone 6 is not updated.

Now my problem is when i restoring back up to iphone 6s plus, when it almost done, there is an error with the message my backup is not compatible with the device or iOS.

As what i know is the new device must have a same or higher version of iOS that the old one, but now my question is that is it necessary to have the same version of iOS with old and new iPhone to do a restore back up? And do i need to update my old iphone 6 to latest version iOS 9.1 and back up to iTunes first before i restore it to my new iphone 6s plus??

Thank you everyone for your help!