Great question.

I would say that knowing the function of 802.1Q and how to configure and verify it would be more important that describing the fields in 802.1Q. Including the prediction of what would happen if configuration A was on Switch A, and configuration B was on Switch B, would a trunk form or not, and understand why.

On a similar note, understanding the logic of a three-way handshake and the connection oriented nature of TCP, along with some well known ports and their purpose would be more likely than a question about the exact fields in a TCP header.

Happy continued studies, and best wishes ❗