Chuwi HI10X CW1529

If this 2n1 is only windows why does it have Linux, Ms-Dos, Andriod and Windows OS selection in BIOS.

Because the tablet uses a universal bios configured for itself, which is used on most Chinese tablets and most functions simply do not responding for anything or can cause problems when turned on.
But you can install android \ dos \ linux if you have enough experience.