At what height, the weight of the body is same as that at same depth from the earth's surface (take, earth's radius = R)

The weight of a body is different at different heights from the earth's surface-why?

At what height above the earth's surface, the value of g is same as that at a depth of 100 km ?

At what height above the earth's surface, the value of g is same as that at a depth of 100 km ?

At what height from the surface of earth the value of g is same as at a depth of (R )/(4) ?

If R is radius of the earth, the height above the surface of the earth where the weight of a body is 36% less than its weight on the surface of the earth is