Rob, most of the time you can get away with not shooting Bias (Offset) frames if you take dark frames, because the Bias is included and removed in the dark frames. But if you take flat frames and don't subtract darks from them, you will need to take Bias frames and subtract them.
ICNR is exactly like taking seperate dark frames except it is automatically removed in the camera meaning you will not need to take Bias frames unless you are not taking seperate Darks for your Flats.
Hope this makes sense.
