Question

why is Ahmedabad in west and Kolkata in the east able to see the noon sun exactly overhead twice a year but not in delhi in the north!???

Answer 1

because ahmedabad and kolkata are present below the tropic of cancer whereas delhi lies above the tropic of cancer.
The states present below the tropic of cancer experience the direct verticals of the sun because our earth is tilted and the areas which are just in front of the sun lies in the torrid zone.
Torrid zone experience the direct and vertical rays of the sun.