What is the expected reaction of a civil airliner pilot upon an invalid request from a fighter jet? After asking a question about the recent diversion/pirating of the Ryanair flight in Belarus (that got closed, but has a nice answer), I got to wonder about how the pilot should have had behaved in that case (fictitious situation of a flight over Lithuania, Belarusian jets requesting it to fly back to Belarus).
What are the rules for a pilot of a civil plane when they are requested by a military plane (a fighter jet) to follow them, when the plane is from another country than the airspace?
I can understand that within an organization such as NATO, a Polish plane could fly over Germany to intercept a Singaporean plane (because of NATO agreements).
From the perspective of a civil airplane pilot - does it matter? In other words my questions are:

is the pilot expected to make a decision about whether to follow a military plane at all? (= if they see a plane that requests them to do something, should they follow the requests no matter what?)
is there any consideration of the airspace? (= should the pilot take into account the place they are above?)

I would like to highlight that I am interested in the rules on how a pilot must behave (and not acts of bravery or something like that).
What do rules have to do with your hypothetical situation?  At that point the question is what a completely unarmed person, who is immediately responsible for the lives of other people (assuming there are passengers), should do when another person who clearly doesn't obey laws and has a deadly weapon demands something, and nobody else has the power to interfere.
It seems to me that the choices available to the civil pilot are to comply, to refuse, or to try some sort of trick.  A rational person at that moment would be completely concentrated on survival for the aviator and passengers, and wouldn't be concerned about rules.