Playing old 90's games on my Nexus? Yes please. Even indie games should run well once DX12 becomes the standard.
Most phones, including Xiaomi Mi 4, run on ARM processors, and therefore despite that the GUI is windows 10, they are not backward compatible with old legacy windows software.
Even if the core was x86 i bet it wouldn't be possible to run old legacy windows software from 90's due to significant hardware differences (where is the 5-1/4 floppy disk ?
Actually, it certainly could be done through either virtualizing the app or through another wrapper. I've seen old DOS games playable through a Java wrapper on an ARM based tablet running Windows RT 8.1. (I ran WC2 on My Dell XPS10 through a web site.) I bet it could be done on a phone fairly easily.
As I understood, the original poster meant to run applications natively.
Of course, it is perfectly possible to run any legacy software if you emulate the legacy hardware. But then you don't really require windows 10 for that, you can have an emulator/virtual machine on top of any OS. There are already DOS / windows emulators for android (e.g. DosBox Turbo, aDosBox, ...) and for IOs (e.g. iDos)