I generally do my briefing AFTER the engine start, as I find 'less' of them jump out and run away!
Probably tongue in cheek. However in my experience it really might not be the best time. You find someone has not worked out how to do up their belt, or has pulled out the head phone plugs or some such thing. Turning around to sort them out is the perfect opportunity to not notice the aircraft creeping forward when you least expect it!
No, you don't have a licence.
Exactly, in this country, which is the posters concern.
Am I right that things are / were different in France - did the Brevet de Base allow students to fly with passengers?