You got WD MyCloud Mirror or so, and you don't have some 3rd party apps - like GIT\Antivirus and etc. If you just take an app from other model, like WD MyCloud EX2 and try to install it on WD MyCloud Mirror you'll see: "Failed to install blah-blah-blah" - FAIL! But!
first of all you need some device,file and tool:
- WD MyCloud Mirror.
- App that you need from other model. it my case - it's GIT - http://downloads.wdc.com/apps/WDMyCloudEX2/git/WDMyCloudEX2_git_1.40.bin
- Hex Editor - WinHex\wxHex\you name it
how to make this works: