Identify the correct statements from the following: I. The ionic radius of Pr$^{3+}$, Dy$^{3+}$ and Sm$^{3+}$ follow the order Sm$^{3+}$ > Pr$^{3+}$ > Dy$^{3+}$. II. Eu$^{2+}$ acts as strong reducing reagent. III. Pu exhibits +7 oxidation state.