HP Spectre x360 turn on legacy boot mode, boot from USB

Why are you searching these keywords?
Why you are not able to boot from USB?
Why you can not set active legacy boot mode?

I have just exact problem and i was clicking BIOS options for hours..
The main problem, the big mistake what i was doing wrong all the time is..
Pressing [Esc] button all the time at the boot or reboot! @#^:o!!!

The point is that if you change [security boot] or [lecacy boot] settings..
Then press F10 to save and exit..
Confirm exit and save with [Yes]..
At the next boot you have to really confirm these settings with random generated PIN code! So..
Do not press [Esc] anymore when boot after fresh BIOS settings change!
You have to Enter PIN code and press Enter to confirm these very sensitive settings!