Click and select the extracted TL-WR850N(IN)_V3_xxx.bin file. Click Upgrade .
No. The TL-WR850N V3 is a 2.4GHz only router. The "Fixed India" firmware does not add hardware features.
For users in India experiencing instability with the TL-WR850N v3 on any ISP (especially BSNL, Airtel Xstream, JioFiber, or local cable broadband), the is strongly recommended over the latest global firmware. If you are not experiencing issues, stick with your current version.
https://static.tp-link.com/2023/202306/20230620/TL-WR850N(UN)_v3_1.6.0_up_boot(230531).bin