The correct options are
A there is a minimum frequency below which no photoelectrons are emitted
B the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity
C even when the metal surface is faintly illuminated the photoelectrons leave the surface immediately
Photoelectric effect supports quantum nature of light because there is a minimum frequency,
corresponding to a photon packet, below which no photoelectrons are emitted.
There is no wave-front concept associated with the emission of photoelectrons. The maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity.
Even when the metal surface is faintly illuminated the photoelectrons leave the surface immediately because emission of photo emission depends on the frequency (corresponding to photon packets) of the light, not on the intensity of it.
Quantisation of charge on photoelectrons have no relation with photoelectric effect supporting quantum nature of light.