Hello,
got my tablet with Windows 8.1/Android 4.4 5 days ago and u can update to Android 5.0 without uninstalling Windows 10. Actually I think it’s not possible to flash the official rom (I also wouldn’t recommend it, cause of the bloatware), so u have to use a custom rom. E.g. Mirek190 V4 Android 5 (tablet must be rooted); u can find this rom in Downloads –> Android Roms.
Unzip the folder and then there’s a discription with the steps u have to follow. So first install the drivers and then run the flash.bat. And there u can select which files u want to keep. If I remember it correctly option 1 is a clean Android install, without removing Windows; option 2 is keeping the Android settings/apps, without removing Windows; and option 3 is a clean Android install with removing Windows. So u have to choose option 1 or 2.
And as dual boot is preinstalled, u don’t have too change anything about the firmware; probably u have to update the bios, but as u’r tablet comes with Windows 10, the newest bios should be preinstalled.
To the keyboard I can’t say anything; din’t even know there’s an official keyboard 😉
Hope that helps 😉