Engineering Bootloader G920F - Downgrade 5.1.1 to 5.0.2

as i said in the title,

i know that there is this engineering bootloader that keep safe the knox status if you want to mod the phone.
my question is simple, if i install this particular bootloader, i'll have root and custom recovery, is it possible to install a rom/custom rom/ stock firmware with the 5.0.2?

thanks.

Good Root Guides for 5.1.1 G920F?

Hi guys,

First post on here ever so excuse any ignorant forum violations.
I'm living the hard life without root and custom rom at the moment but hoping that can change.

Anyone able to point me in the direction of a good guide/ guidelines for rooting the below?

Model: SM-G920F
Version: 5.1.1
Build Number: LMY47X.G920FXXU2BOG8

Would also be good if we could get a list of the best step by step rooting guides going - specifically from the initial rooting phase right the way through to flashing a rom.

Thanks in advance!