danielNC:
Why does the function of Pin 1 differ on the Uno/Decil as opposed to the MiniPro?
It doesn't. So something else is wrong. Perhaps pin 1 is damaged.
danielNC:
DO I address A6 and A7 as pin number 20 and 21? Can't find much info on this...
You address them like the another analog pins "A6" and "A7". There are constants defined for all of the analog pins.