Nop, is again supported now, is Windows Phone with Windows 8 that was cancelled since a few moment...
I siwtched on my old Lumia 550 lately...just to get updates. Beeing at 1709 (10.0.15254.600) now it doesnt offer any more recent updats though. Again supported now ? Even my Lumia 550 ? @_@
Sure, if you want a platform with almost no developers, no support for popular apps and is dead before it even releases, like Windows phone/mobile was
Not really, but makes more sense than choosing an already obsolete platform / device... Plus with Android you have XDA if you need more than 2-3 years support, and iOS supports devices for many years so not sure where your argument is heading but doesn't really hold up
On Android you would have access to Microsoft Launcher Preview. Do a Search on Microsoft Launcher Preview. It might be something you could find interesting.