I'm from a Cambridge background, not Oxford, but the trick to this sort of essay is that the journey is the destination. That is, ultimately it's not expecting you to reach a single right conclusion, but to present evidence, argument, and references.

The rubric doesn't say, but I'm guessing you'd get three hours per essay, one hour per question, minus the minutes spent selecting which ones.

I don't know, but many of them have a triggering smell, which must be on purpose. A polarizing prompt might show you what somebody thinks, but it is also likely to show you whether they think at all. I'm reminded of "This I Believe" on NPR. The subject is what a person believes, not what they don't believe.