OK, I had completely overlooked the double row.
Given the mechanical arrangement of the connecting rods, each row will do that described above, it's just how the two rows are interleaved with each other.
I have to say I don't actually know the answer to this supplementary point so will leave it to others. What Jhieminga writes looks right. The shape of the crankshaft will give the answer. It would be interesting to know the firing order for the R-4360 (four row) as well.