Thank you very much for the guide finally I got the bifurcation working. I got that what BIOS build date it is showing is nothing to do with pcie bifurcation. First tried with all slots set to x4,x4 or x4,x4,x4,x4 modes and in the both optimal and fail safe settings, Then I dialed back to auto for the slot I need bifurcated. I find out that maybe hwinfo and bios tool show cards in reverse order, Hence I was not able to achieve it earlier.
However I done it on old BIOS, I will be grateful if I get Any help to achieve same on newer BIOS. Is there a chance if there is a newer AMIBCP tool available which can open newer BIOS files without error?