How to restore a backup from an iphone 6 to an iphone 4?

My iphone 6 had been water damaged and is no unusable. I had recently bought a used iphone 4 as a replacement. I had it activated and it is working fine. When I try to restore a recent backup of my iphone 6 to my iphone 4, it doesn't show up in the list and only shows really old backups from when I had an iphone 4S back in the day. Does anyone know of a solution to this? Tried a method that edits the info.plist. It did show up on itunes but reported an error stating corruption or incompatibility with my desired backup. Please let me know, thanks!

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You can try to do an iOS upgrading before you restoring a backup.