No, you can't spot a memorized story. You can possibly spot a poorly memorized story. It's the difference between learning a speech off by heart and knowing the material backwards.
Without probing questions, no. On technical matters and some interpersonal matters, though, you can use a variation of 5 Whys to quickly drill down on certain decisions or details. The only way to pass that is to actually know what you are talking about.
Exactly. Memorize the incident, what you want to convey about it, and how to emphasise your angle on it. Don't rote-learn a single telling, and don't blow it off and think "ok I'd talk about that time I saved the orphans, next!"so that in the interview you're all "I was on my way back from preventing a bank robbery...wait no, it was a mugging...and i went past the orphanage on 5th Ave, or 6th, you know the one?"
