BAW001
1- As this incident highlights, unlikely with planned 'destination' fuel; but with any diversion it is, Captain/Crew, Airline and most importantly, fuel dependant.
(a)– That is the job of the UK Civil Aviation Authority as the regulator.
2- As per 1 (a), plus Unsure/Unlikely.
Great questions and I would suggest a chat with the CAA if you want more information on what is actually happening.
Great debate!