I don't think the asking questions/getting seatbelt stuck/being asleep when the food comes is anymore likely to come from an older child than an adult tbh.
Flying isn't something 'everyday' for most people, so it does happen that people get confused anout the seatbelts, or where the loo is, or how to work the entertainment, or the seat etc etc etc and the natural thing to do, if there are no stewardesses around, is to ask the person next to you for help.
I think you are a bit mean if you begrudge answering a couple of questions for the person next to you durig a 12hr flight.