Question

where is the value of g maximum and minimum at the surface of earth​

Answer 1

g maximum at poles and minimum at equator on the surface of earth .

Answer 2

G is a universal constant and does not vary anywhere including the Earth’s surface. You must mean, instead, the gravitation acceleration on earth which is about 9.6 m/s and this only varies ever so slightly on earth due to the moon and the sun which is why we have tides.

Hope this will help you