A scalar quantity is the one that is conserved in a process : The statement is false. It is because kinetic energy (scalar quantity) is not conserved during inelastic collision.
A scalar quantity is the one that can never take negative values : The statement is false. It is because the temperature (scalar quantity) can be negative.
A scalar quantity is the one that does not vary from one point to another in space : The statement is false. It is because gravitational potential energy (scalar quantity) vary from point to point in space.
A scalar quantity has the same value for observers with different orientations of the axes : The statement is true because the value of scalar does not change with orientation of axes.