There is limited fuel, a hijacker of any persuasion isn't going to ignore that fact.
Unfortunately not so. Some hijackers have no interest in making a successful landing, Ethiopian B767, for example or, more obviously 9/11.
Others have shown no realistic appraisal of an aircraft's range capability, ordering crews of short haul B737 over Europe to fly direct to the Middle East and been unable to comprehend that a landing for refuelling would be necessary.