As a Brit, but not a teacher, I would offer the following:
Hope this helpsHello, Teachers.
It is 2 o'clock now, and he will come back in two hours.
Does the above sentence mean 'he will come back after 4 o'clock' or 'he will come back during the time between 2 o'clock and 4 o'clock'?
Yes! Effectively both are correct, with the proviso that the person will be back within 2 hours, but that it is more likely to be around 2 hours before he comes back i.e he would be back around 4 o'clock.
He stayed in water over five minutes.
Does the above sentence mean 'he stayed in water for more than five minutes' or 'he stay in water during five minutes'?
Similarly, this means that he stayed in the water during and for more than 5 minutes.
Do '2 hours after/before' and 'after/before 2 hours' have the same meaning and usage?
a) He left 2 hours after/before [I left].
b) He left after/before 2 hours.
a) really needs something else to complete the sentence, whereas b) doesn't. (He went to the party, but left after 2 hours)
Is the following sentence correct?
They will arrive 2 hours after/before he wakes up.
In my experience, phrases like '2 hours after/before' can only be used in a sentence in the past tense.
A is at home asleep. B is flying in from elsewhere.
B will arrive at the nearest airport to A 2 hours before A wakes up, but it may take B 3 hours to get through immigration and drive to A's place.
Student or Learner