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The purpose of Q33 is to add a voltage drop along with D41 to lower the voltage at the gates of Q38, Q40, and Q42 (this is explained in the Design guide). I would assume D42 is for the same purpose, to lower the gate voltage for Q39, Q41, Q43.
The purpose of Q36 is to expedite to extract and exhaust the charges on the gate of Q39 so that the cut off speed of Q39 can be desired for actual application, adjusting the value of R91 can change the FET cut off speed.
