I can confirm that on Mi3 LED notifications don't work. (except for charging and LED testing)
WiFi works well though. I can connect to several networks without any issue. 2.4Ghz and 5Ghz.
Flash 5.12.17, reboot, flash 6.1.21, reboot - done. no need to do anything else.
you don't need to flash 5.12.17 twice. the reboot after 6.1.21 install is important.
After updating Mi3w to 5.12.17 it still shows 2 boot options in recovery.
Is that meant to be like that, even though partitions are supposed to be merged?
The Antutu Benchmark wont change much from Dev to Stable ROM. Because the Hardware is still the same!
Same as with battery life. Unless they did some major change in display on time or brightness, there wont be any difference.