This, 100%. A full-stack engineer will likely have at least a solid understanding of the HTTP protocol, HTTPS, WebSockets, the interface layer between the frontend server and their chosen Web webdev stack, and so on. Then a more general understanding of networking protocols, TCP vs UDP, DNS, routing, etc. In general, you need to have a solid understanding of the layer below where you're working, some understanding of the layer below that, and so on, less and less detail needed for each layer down.

(That's not to say that you shouldn't bother with learning more -- more knowledge is always good -- or that the OP specifically only knows that. It's more a sensible minimum.)

My own "curriculum" for that has been Jeremy Howard's Fast AI course and Sebastian Raschka's book "build an LLM from scratch". Still working through it, but once I'm done I think I'll be solid on your point 2 above. My guess is that I'll want to learn more, but that's out of interest more than because I think its necessary.