How can we measured the volume of spherical object?

You do need to be more specific, the volume of a sphere is V = 4/3 π r^3, it does not need to be related to a cylinder. So if you know the radius, you can calculate the volume. The volume of a cylinder with the same radius and with a height of 2r (since it would be the diameter across) would be V = π r^2 h = 2π r^3.

No it doesnt because it can be any number.

Shy diving is the only sport which doesnot require a high level of physical fitness