The only question you listed that an interviewer may not ask is the one about depression, as you cannot inquire about a person's medical history or needs.
Aside from that, interviewers want to throw you off. They want to see how you respond on the fly. While conducting interviews, I have asked questions ranging from asking them to describe someone they once bullied, to 'Kirk vs. Picard', and even whether they thought they could beat me in arm wrestling. It all may seem nonsensical, but the idea is that these are questions a candidate would not of rehearsed for and so you can get a real judge of their character.
Onto your last statement, generally interviews are not conducted in direct sight of others, so I would not see how your friend would be aware of this. Plus, as you said, the friend lives with depression, so more than likely they saw the interviewer as being opposed to them only in their head. People with depression are like that. In reality I'm sure the interviewer was indifferent.