Gen 3 prius 2013... code C1202 questions!

I'm sure the system must hold fluid from each cylinder all the way back through the actuator the accumulator all the way up to the reservoir of fluid that has to be complete and stay full if it goes down it needs to pull from the reservoir with no air so I would assume in the reservoir and accumulator and all those places there is brake fluid and no air in the system throughout I don't know how much the accumulator or the actuator would hold but you don't feel it separately I hope.

 

The C1202 is intended to warn you about low fluid in the reservoir, but if you are seeing a proper fluid level there, then it is probably an issue with the level switch or its wiring.

That is probably unrelated to a C1391 or pump cycling; they'd just be separate issues. If the reservoir level really were very low (enough to allow air in), that could be a different story, but a simple issue with the level switch isn't going to cause pressure to bleed off.