I wish this help you It's better to install Windows 10. Even though documentation says you can develop UWP on windows 8.1, you won't be able even to test it on windows 8.1 PC. You'll need physical remote PC with windows 10 to test your app. You can't deploy windows 10 app on windows 8.1 PC since they have different API. Limitation from link:
I wish this helpful for you At the lowest level, WinRT is an object model defined on ABI level. It uses COM as a base (so every WinRT object implements IUnknown and does refcounting), and builds from there. It does add quite a lot of new concepts in comparison to COM of old, most of which come directly from .NET - for example, WinRT object model has delegates, and events are done .NET-style (with delegates and add/remove subscriber methods, one per event) rather than the old COM model of event sources and sinks. Of other notable things, WinRT also has parametrized ("generic") interfaces. One other big change is that all WinRT components have metadata available for them, just like .NET assemblies. In COM you kinda sorta had that with typelibs, but not every COM component had them. For WinRT, the metadata is contained in .winmd files - look inside "C:\Program Files (x86)\Windows Kits\8.0\Windows Metadata\" in Developer Preview. If you poke around, you'll see that they are actually CLI assemblies with no code, just metadata tables. You can open them with ILDASM, in fact. Note, this doesn't mean that WinRT itself is managed - it simply reuses the file format.
Start Store Apps - Universal Apps for windows phone 8.1 and windows 8.1 application
I think the issue was by ths following , As you surmised, Universal Drivers mean that the drivers can run on any device running Windows 10 (PC, Phone, IoT, etc. -- in theory Xbox as well but that's a closed platform). A Universal Windows App can also run on any device running Windows 10, but it can't contain drivers; drivers must come from Windows Update or from a legacy installer like MSI for the desktop. Whether or not your Universal App can talk to your Universal Driver depends on whether you need to pass Store certification or not; how the driver is exposed (eg, via HID or something else); etc.
Keyboard layout change not detected in universal windows apps with C#
it should still fix some issue In Desktop, we use the Input Method Manager to communicate with an input method editor (IME), which runs as a service. In UWP, we should be able to use the Text Services Framework. There is a document about Alternatives to Windows APIs in Universal Windows Platform (UWP) apps. So we should be able to use the Windows.UI.Text.Core namespace, it provides types for accessing the Windows core text APIs and the text input server. Windows core text is a client-server system that centralizes the processing of keyboard input into a single server.