The Union Flag
Yes, usually the remaining airworthy Lancaster and 4 Spitfires fly formation for the Queens Birthday and a few other special occasions.
They fly a different flag, because they are a different country, now if they were the same country, they would fly the the US flag.
It could, but it would be disrespectful.
Any flag could, but it would be disrespectful.
Flying an United States Flag upside down is a recognized distress signal.
It is not illegal to fly a tattered flag, but it is considered disrespectful. It is recommended to replace a tattered flag with a new one to show proper respect for the flag and its symbolism.
it is bad to fly a flag when its war, because it just is
Technically, they are on their own soil, so no, they don't have to fly our flag. Just as our embassies don't fly their flag.
It would be respectful, but is not required.
Since there is no wind on the moon, any flag "flying" would have to be due to mechanical support -- exactly as was stated as having been done in 1969 (I recall that as I watched the flag being "unfurled").
When somebody has died.
British flag