I you put the device into recovery mode and use the USB load. You can use the "adb sideload xxx.zip" and this will allow you to update the os.
Thank you for your answer, but from that recovery mode, I only have access to "Apply from SD card" and "Reboot".
That is why I was focusing more on Fastboot.
Thanks again for your help
sideloading is not currently supported on our devices, The bootloader is also locked.
btw, the latest version of fastboot supports, an option for vendor ID.
eg, fastboot -i 0x05e0 devices or fastboot -i 0x0414 devices.
but like I mentioned it is locked.