Here you and different Windows Phone and Firefox OS and of course Android 2.1, Jelly Bean, KitKat, and now Lollipop Marshmallow. However, it is recognized that the launch of these systems does not mean their complete and bug free work.
the HTC HD2 was released in 2009. The smartphone runs under Windows Phone 6.5. And it is unlikely that HTC could have imagined what fate awaits this gadgets. It turned out that he still lives. Moreover, the unit during its existence managed to try on a bunch of different mobile OS and still easily runs the latest version, for example, Android 6.0 Marshmallow.