The statement I is correct but rest is incorrect and it can be corrected as,
From the given graph, we can say that we have obtained different values of stopping potential but the same value of the saturation current for incident radiation of different frequencies. Since, the energy of emitted electron depends on the frequency of the incident radiations. This means, stopping potential is more negative for higher frequencies of incident radiation. Thus, we can conclude that,
(I) stopping potential are in the order ,

if the frequencies are in the order .
(II) This further implies that greater the frequency of incident radiation, greater is the maximum kinetic energy of the photoelectrons. Consequently we need greater retarding potential to stop them completely.