You may be able to recover some of this content from your photo stream.
My Photo Stream FAQ - Apple Support
You should have taken the opportunity to copy off all of your photos and videos using Windows Explorer before deleting them from the iPhone.
I suspect changing the phone name won't have made any difference, it will still have been recognized as the same device. Restoring as new device before changing the name while setting it up might have worked, whether you had used iTunes, or General > Reset > Erase All Content and Settings on the device.
iTunes normally creates one rolling backup per device. This backup is updated when you manually backup, or at the first sync on each calendar day. Mac users can instruct iTunes to make a copy of a backup set but in Windows the way to preserve a given backup set is to restore it to your device. After the restore the original backup is renamed with the date and time of the restore and a new rolling backup is created for the device.
I would recommend you untick any option that causes iTunes to start or automatically sync when your device is connected on the device's summary page, and under Edit > Preferences > Devices tick the option Prevent iPods, iPhones, and iPads from syncing automatically.
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