On weightlessness.

Yes, the gravity force inside a spherical shell will be zero.

But note that we are talking of the force on the body due to the spherical shell and not due to the earth. Since the earth will exert a force on the body it will not feel weightless.

If you were to think of the earth itself as the sphere under consideration, then at the centre of the earth the force will be zero and the object will be weightless.