P Block Elements

What are the correct statements about the elements of group 13 given below?

(I) The stability of +1 oxidation state follows the order $\mathrm{Tl}>\mathrm{In}>\mathrm{Ga}$.

(II) Boron has the lowest melting point and boiling point as it is a non-metal.

(III) Boron shows a maximum covalency of 4 in its compounds.

(IV) The order of atomic radius is $\mathrm{Ga}>\mathrm{Al}>\mathrm{In}$.

(V) Aluminium is passive to concentrated nitric acid.