Identify the correct statements about lanthanoids

I. $\mathrm{Ce}^{4+}$ and $\mathrm{Tb}^{4+}$ act as oxidising agents.

II. $\mathrm{Eu}^{2+}$ and $\mathrm{Yb}^{2+}$ act as oxidising agents.

III. Misch metal is an alloy of $95 \%$ iron and $5 \%$ lanthanoid metal.

IV. $\mathrm{La}^{3+}$ and $\mathrm{Ce}^{4+}$ are diamagnetic in nature.

Match the following

The correct answer is

Observe the following $f$-block elements

$\mathrm{Eu}(Z=63) ; \mathrm{Pu}(Z=94) ; \mathrm{Cf}(Z=98)$;

$\operatorname{Sm}(Z=62) ; \mathrm{Gd}(Z=64) ; \mathrm{Cm}(Z=96)$

How many of the above have half-filled $f$-orbitals in their ground state?