Forza files encrypted

Hello guys, i just moved to Windows 10 few days ago in my two PCs. First i installed Forza to my main computer and some days after tried to copy/paste the folder from PC1 to PC2 instead of redownloading whole thing.
There i encountered my first problem, Forza files are all encrypted and when i tried move it to PC2/windowsapps was denied.
After that i decided to enter insider preview with PC2 and the folder with Forza unfinished download become uncrypted, i just dont know how and why because i tried decrypt it before but system always denied decryption to Forza folder.
With preview Build uncrypted folder released to copy/paste my backup Forza game from PC1 to PC2, Windows store installed it and game runs fine.
After that i discovered than now my Forza game in PC1 becomes broken and need to redownload.

UWP supposed to unable backup from games?
Is there something i doing wrong to use my backup in other computer?
Windows 10 update feature says it can download updates and apps from other computer which already have files but it not working in my home network, always make full download from internet.

Will be glad if someone can explain this questions.

I don't believe UWP games support backing up yet, as I've tried the same thing with Quantum Break and it's never worked for me.

The Windows Update feature you are referencing is just for downloading Windows updates. It doesn't include Windows Store apps and games, as far as I know.