The Windows 10 mobile SKU is aimed at devices where running Win32 apps doesn't make sense, so it won't support a desktop mode. It will be customized to run "Modern"/Universal apps from the unified Windows Store. The Mobile SKU is aimed at devices with small RAM and disk requirements. It's built for locked down devices, though, in theory at least, it could run on a device with any size screen.

The Windows 10 Desktop SKU will be the more general purpose SKU. It will run on anything with an Intel chip, just like Windows XP, Windows 7 and Windows 8. The Windows 10 Desktop, technically, will be able to run on devices of almost any screen size (including existing 7-inch Intel-based tablets, as Microsoft's Joe Belfiore tweeted yesterday). The question is will most users want to look at Win32 apps on screens that small? If they do -- and if OEMs think there is a market for small Windows 10 devices that can run legacy apps -- new, small-screen size Windows 10 devices running Windows 10 Desktop will come to market.

So, the Windows 10 Desktop SKU can run Modern/Universal and Win32 apps in either tablet (full-screen) or desktop (windowed apps) modes. The Windows 10 mobile SKU can only run Modern/Universal apps and only has full-screen app mode.

Meet Windows RT series 2 aka Windows 10 mobile SKU.

Microsoft will demand it to be installed on anything with 7" screen or lower (even if it has HDMI output).

It is also their second step in "free Windows initiative". Big discounts and free offers will be available to manufacturers who will accept idea to install as much restricted SKU as possible. I am sure we'll see even large tablets with RT Series 2.

My opinion is that any good government must FULLY prohibit any company to limit software distribution on their devices. Including fully banning any special software shops like Google Play or App Store.