Hi guys, TP-link utility doesn't support soft ap on windows 10. You may use a third party utility, such as connectify.

Is your adapter V1 or V2? You may try use the driver from Ralink. Chipset Ralink RTL8192CU for V1, RTL8192EU for V2. http://www.usb-drivers.org/realtek-rtl8192cu-wireless-driver.html Fix the router...

No way to change the mac. Mac address likes personal ID. Every network device has its own mac and can't be changed because it is inside the chipset. If your TL-WA850RE has a green web UI, can you...

Not sure, it is safer if you can buy the modem router in India.

I don't think so because the product is a little old.

Is BSNL providing ADSL or VDSL service? if they are giving ADSL service, you may check with TP-Link Tech support about this.