My Doubts about Power Amplifier Circuit

Good day,friends

I have a problem on analyzing the following circuit which is power amplifier based on 2N3055 ( The datasheet of 2N3055 ) with different multi-amplfier and I don't know how I resolve these.Could someone here give me some feasible advice?

(A) There iss a CE one stage after of different amplifier however I don't know why used this and why used capacitor?
(B) After of last stage there are two diode junction on transistors and (variable resistor 100 ohm) and I don't know why used this on this stage ?
(C) On next stage that there Is a power amplifier I don't know how it work?

Thanks in advance！