OT, cooking hamburgers, microwave stuff

1) hamburgers, especially thin ones, in a skillet.

If I cook the hamburger on one side for say 4 minutes and then on the
other side for 4 minutes, how does that compare with 2 minutes on one
sdie then 2 to 4 minutes on the other than back to the first side.
Does it take only 2 minutes more to get the same result as 4 minutes in
a row, or has the first side cooled off by then, when it was on the
other side, so that I should cook it longer if I've flipped it too soon
earlier????

2) related question about microwave cooking. Say I cook something for
8 minutes in a microwave, take it out to eat, and after a few minutes I
decide it hasn't been cooked enough. When I put it back, do I cook it
for the same length of time I shortchanged it by earlier, or has it
cooled off in 5 minutes and I need to cook it longer?

Does it make a difference if I'm just heating something versus cooking
it? ISTM, it has to reach a certain temp or more to start cooking, so
I have to microwave it longer total, if I take it out in the middle.