Assume I check in on-line for a return flight with BA and then am unable to make it to the airport. My booking has zero flexibility.

Will I earn Avios miles and tier points from this return flight if I do not fly it, even though I have checked-in online?

If I check-in online and do a no show, will I receive the same refund as if I had cancelled the flight rather than checked-in online?

Thanks.