Hi Samarth,
HP will sometimes lock the advanced BIOS if they feel that anymore adjustments would do your system harm. I did find the steps below to help you confirm if this is the case with your system.
To Access Advanced BIOS Settings in HP
# Restart your Computer. Stop whatever you are doing.
# Enter BIOS Settings. Press the Esc key repeatedly until the Startup menu opens.
# Power Off/ Restart your Computer. Power off or restart your computer again, and this time press F9.
# Press F10 and Get the Advanced Tab.
If this still does not work then your Advanced BIOS is locked and according an HP forum, there’s no way yo unlock it.
Good luck.