Renegradenick

Hi I'm new to bios unlocking but pretty experienced with building computers and computer in general. I have a Lenovo Y480 and a 640m Le in it. I would like to overclock it. Do I need to unlock the bios in order to do that or can I just use nvidia inspector or msi afterburner? I have 5dcn40ww which I understand is version 2. What is the best option to unlock the bios? Upgrade to 8 or stay at 2 and how would I do that. Is this unlocked bios compatable with 640m le and will I be able to set my own clock speeds, memory, etc? Thanks in advance for the help.