Can I combine backups from both an older device and a new device?
iPhone 6s Plus
No. A backup can only restore an entire device. When you restore to a backup, it takes the device and puts it to the way the device was at the time of the backup, and anything that may have been done since that backup was taken would be deleted. Also, you cannot access the backup file to change or modify contents like you can certain other files.
I believe that you can only do one backup from iTunes per device. I believe that backups are handled by iTunes, not iCloud.
A metaphor is: ICloud is the folders; iTunes backups are the whole file cabinet.
You do have the ability to backup your iOS device, and also your OS X computer to iCloud. What it backs up differs from what is backed up in iTunes, but there is a way to back up to either. However, as I indicated in my earlier post, there is no way to mix content in two backups. This will help you understand the difference in the two backups and how to accomplish them in iOS. About backups in iCloud and iTunes - Apple Support
Can I combine backups from both an older device and a new device?
