Flight deck visits
I can confirm that the chances of you getting a visit in flight are, well, ZERO.
As a PPL student, I have often written some questions for the pilot, and asked the cabin crew to hand it over. Often some techie questions mixed with some jokey ones too.
I awlys get a reply, but often not what I was looking for, and have had a few invtes to pop my head round the door once landed and parked. and i can say the crew I have chatted to had an interest in my limited flying as much as I have in theirs.
So to those pilots I have met this way, many thanks for your time.