Gold sol is not a

Consider the following statements about the Tyndall effect:
$(I)$ It is used to distinguish between a true solution and a colloidal solution.
$(II)$ It is possible only when the refractive indices of the dispersed phase and the dispersion medium differ significantly.
$(III)$ It is observed only when the size of the colloidal particles is much smaller than the wavelength of the light used.
Which of the following statements are correct?

Which one is an example of a multimolecular colloid system?

Which one is an example of a micellar system?

Explain the purification of colloidal solutions.

What is the coagulating power of an effective ion carrying a charge opposite to that of the sol particles called?