With the Code, what are Pre Amp, Power Amp and Cabniet, and what do they each do? Do they all have to be on? I don't know much about Amps.
Guitar's pickups provide a weak eletrical signal that must be transformed in a strong electrical signal required by the speakers to move themselves.
The amplifier does this transformation.
[to be continued]
An amplifier is made of two main circuits:
1) the preamp which performs a first amplification of the "weak" guitar signal into a "line level" signal and besides it shapes the tone by applying the equalization (the classic low, mid and high potentiometers);
2) the power amp which performs a second amplification of the signal: from line level to "power level" needed by the speaker.
Last element of the amplification chain is the speaker, which uses the electricity received from the amplifier to move the cone and thus creating the sound
(best said "recreating" the sound of the guitar strings).
So the answer to the OP question is:
Yes, they all must be on.
