If you all you could see were their penis or pussy, could you pick your partner out of a line up? No looking at photos for reference, just from memory. Would they need to be hard/aroused for you to recognize them? What about previous partners?

I think I probably could pick out my partner's pussy both aroused and not. The way her labia sit is very distinctive. I doubt I could still recognize previous partners, maybe I could when we were dating.