I am very very very very grateful to you mate. I can't express in words how happy I am. I was literally searching on YT for past 7 hours and nothing worked, but this one got me. :) Life savior!
Sorry but my only boot device options for HP elitebook 850 G2 are Notebook Hard Drive and Notebook Ethernet although I have plugged in a bootable usb stick with Batocera on it. I am really frustrated now having tried for hours...