Problem:

I have laptop of HP, I am trying to install windows from USB, but not sure
which Function Key will be used, to choose boot option.

I tried several keys randomly, like F12 and f2 etc.

Solution:

If you are not sure, which key will be used to change boot menu of the laptop.
just Restart your or On your Laptop and press "Esc" button. you can see diffrent options
and helpfull keys related to your laptop.

in my case F9, is working fine to change boot sequence.