If you drop them all the way from the top of the stack, this is what happens

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The mixer step seems unnecessary at this stage, other than that, checks out

This whole circuit is cursed… it looks like for Q19 to be on, the base/collector junction of Q18 must be forward biased - is that even allowed? Does that make the collector a fourth emitter? Or is the whole circuit just made to convey to the reader of the datasheet that they could never ever build this themselves?

There’s just one collector though?