The micro usb port cannot access the serial ports - only supply 5v power to the board. However, I've managed to flash the chip using my own CH340 usb to ttl module via the GPIO pins and the flash was successful and the chip is working (although the usb to serial is still not working).
I didn't receive the item. I agree not the seller's fault (which is why gave 4 stars rating) as they posted it and it showed as being delivered by the postal company. But I didn't receive the item and I'm now out of pocket. Raised issue with Ali Express who say can't do anything as showing as being delivered. Disappointed as waited 3 weeks for item and wasn't received.