User Manual

Because of the Arduino official updated the IDE's default Nano BootLoader, so
your code couldn't be uploaded on IDE 1.8.5 and up.
If your Arduino IDE is 1.8.5 and up, you select "Old BootLoader" in the IDE's
processor:
If your Arduino IDE is 1.8.5 or below, you select "ATmega328P" in the IDE's
processor:
Question 2:
I tried to run the code but the Arduino cannot detect the board (there was no