Hello , I had a “virgin” teclast x98 air 3g (c9j6 – dual os – 64gb) and decided to:
1)update bios to 2.02
2)install android 5, mirec v6 rom, repartitioning the tablet and wiping all partitions….
After that, when booting windows logo has dissapeared and i cannot install windows on it…
Make a bootable windows 10 usb key / drive and plug it in while starting, when in the boot menu there should be a logo on the right of the android one. I cannot help further since i do not own one but I think you just have to install windows that way. Be careful not to delete android while reinstalling windows.