Powering Boron using 12v

12V on a Xenon or Argon on VUSB will be immediately fatal to the device. Also do not power both VUSB and the micro USB connector at the same time on a Xenon or Argon.

12V on a Boron on VUSB will be OK, as long as you don’t have any other circuitry that is expecting VUSB to be 5V maximum. The reason is that the Boron has a more elaborate power manager IC (PMIC) that is basically the same as the Electron and E Series and can tolerate higher voltages.