Maybe you get some help from here
https://xiaomi.eu/community/threads/redmi-4-prime-bricked.37822/
I had a similar problem on my redmi 4x years ago and the problem was that I didn't have the correct drivers installed so miflash didn't detect the smartphone as a a COM port and didn't let me...
There's no difference with the version without the b20 band as far as I know, just click one of the links in the first post and look for the redmi 4x version that is named HM4X
Enviado desde mi Redmi 4X mediante Tapatalk
He is talking about the redmi 4x (santoni) with SD 435, not the redmi note 4x, but anyways there's not a different ROM for the model with b20
Enviado desde mi Redmi 4X mediante Tapatalk