I am not an expert and don't play one on TV
OK, Let's see what I can answer:
There are 4 buttons to the left of the timer dial: there are two speed buttons, regular fabrics and modern fabrics. The next two are suds return and normal fill. The suds drained through the suds hose. If you wanted it saved, you put the stopper in the drain of the sink or tub. If you wanted to reuse suds, you pushed suds return, started the machine and an electric pump pumped the suds back into the tub. Pushing normal fill filled the washer from the inlet valve.
Now about the lid and the reason I hated early Maytag washers even before I could see how poor the agitation was. Instead of doing things the right way and either having a solid tub with timed or metered fill or a perforated tub in an outer tub with a pressure switch, Maytag had three tubs: the basket for the clothes, the close fitting solid tub (for the dirt as Maytag said) and then a large water container or drain tub. Because the tub that held the water was bolted to the inner basket, it could not be fitted with a pressure dome for a water level control. Because Maytag was too good for timed fill until the A4MP, they had to come up with a way to measure the water level in the tub. That was via a float and later a rubber diaphragm in the agitator that moved the metal cap up and down against the round button in the lid. This caused them to have to use all kinds of complex switches and circuitry in the lid to not only measure and react to the water level, but also to shut off the power if the lid were raised because if the power was not shut off when the lid was raised, the little round button connected to the water level switch would flop down like an outtie belly button and the water level switch would call for more water when the machine already had enough.
so there was a mercury switch that responded to the lid's vertical or horizontal position to close the circuit in the down or horizontal position and open the circuit in the up or vertical position. The water level dial under the lid adjusted the pressure on the water level sensor to allow partial fills. The early Maytags were almost alone in the automatic washer field in that they had no way of operating with less than a full tub of water (12 gallons). When the water level switch came out, Maytag was quick to offer a retrofit lid kit to allow the older machines to have water level controls. I have never seen an older Maytag with the retrofit so I can't say how popular they were. The tub was so small and the agitator fins so large that you almost had to have the tub full of water to prevent fabric damage, besides the damage from detergent burn from the detergent sitting on the fabrics during fill and the damage caused by the agitator stopping when users lifted the lid to add bleach.
Owners of the older machines bitched that when they went to buy a new one the wash time was shorter, although even into the mid 60s, the A500 offered the 14 or 15 minute wash time. My timed-fill only offers a 10 minute wash, maybe because part of the wash time was used for the timed fill.