Luckily we aren't a casino so won't be round to empty your wallet - ADC0 is actually A.0, Download Serial Out (leg 19).
I can't recall if I have ever tested what making that pin an ADC actually does. I expect the firmware either masks out that bit or setting it as output keeps it as a digital output.
C.6 (leg 4) is the MCLR/Reset/Programming pin on the underlying PIC which is digital input only and does not have ADC capabilities. If it did we would have made it available because there'd be no reason not to.