Is it normal that the Microsoft apps like Windows Movies and TV app don't play MagicYUV codec?
I especially need Resolume Alley to play these files, but when the OS doesn't know the MgicYUV codec, it doesn't work.
It depends on whether those apps use Video For Windows (VFW) interface codecs or not. MagicYUV on Windows can be used by apps through the VFW interface in general (apart from VLC). If an app is not using VFW, then it can't decode MagicYUV files. It all depends on the application. Some can only use their built-in codecs.
I don't know how Resolume Alley decodes it's files.
On Windows, you can use Windows Media Player, Media Player Classic, VLC to play MagicYUV files, but there are many other players which can play them.