I would want to talk to Cain following his exile from Eden. He built his own city from scratch, no help from family or anything. That's some serious ingenuity.
I'd want to know what kind of city planner/leader he became following his punishment. What kind of things would he prioritize. What roles would have been the most prominent in such a city. There's a lot of questions one could ask.
I guess if I had to narrow it down to one, I'd ask: how did your punishment influence the type of city you would build?