Another problem is that phones running 5.1.8.0G cannot find and track locations properly. Tnis is easily visible when using location-based apps such as Google Maps.
This issue was first introduced in 5.1.7.0Y and has now been transferred to 5.1.8.0G. The only solution is to keep the phone on 5.1.6.0G and not update to 5.1.8.0G.

If band20 unlocked by software, can this phone work on band20?

I recommend you to do a clear update with latest firmware. Because I have a MX5 and using Flyme 5.1.8.0 and have none of these problems. And I live in Turkey but because you wrote this thread in English, I write in English too :).

on m2 note icons are now smaller,why they do that,and option in settings for smaller or bigger icons not working

Line App could not share location.It always shown up message "We are currently readying this function.Thank you for your patience."

Ι installed 5.1…8.0G and i choose via the facebook to see a video with youtube but instead to open up the application this opening with browser