I had a laugh :)
HG : Heat gun (an alternative roasting method)
As far as the cracks go..... (I might be wrong so pls correct me if required)
*Note coffee beans crack twice
FC (first crack) yep when you get the first discernable cracks.. it then becomes rolling first crack when there is a flurry of cracks then there is a break and you get second crack which sounds different to first crack and then rolling second crack is when you get the next flurry of cracks.
Most people roast before/to/some period after second crack which is why it is mention so often.
When you first roast (I know I did) I mistook rolling first crack for second crack and ended up with a highly acidic brew.