2009 MacBook Pro does not respond to the Option/Command keys on boot up I want to flash my 4.1 to 5.1. I then want to turn off SIP. No matter what I do, different keyboards tried, different USB ports, nothing I do will let me boot off a USB drive, or into OS recovery or OS Utils.
If you have a USB keyboard and have tried each port in a row, then the USB / logic board are the problem.
Even a PC keyboard will work to option boot - so even a PS/2 keyboard will work.

Using CMD on Very Old PC Keyboard During Boot

As above, only a quite rare keyboard won’t work with modifier keys that don’t work on Mac firmware.