The 70s.
the president serve for four years in the united states.
No, that is not a requirement.
4
44 presidents but not all of them serve their term
If they do not get nomination of their party it is impossible for them to serve.
State which one(s)
Yes They Did
no
Presidents can only serve for 2 terms. 4 years are in a term.
George W. Bush and John Q. Adams did not serve as vice presidents. Note, George H. W. Bush and John Adams did serve as vice presidents.
One
Washington and Adams