Which of these statements is not true?

Which of the following will not act as an oxidising agent?

Describe the chemical reactions of the lanthanoids with $H_2$ and $O_2$.

The correct statement about $Cr^{2+}$ and $Mn^{3+}$ among the following is (Given,atomic numbers of $Cr=24$ and $Mn=25$)

Which of the following will act as the best oxidizing agent?

How would you account for the following:
$(i)$ Of the $d^{4}$ species,$Cr^{2+}$ is strongly reducing while $Mn^{3+}$ is strongly oxidising.
$(ii)$ $Co^{2+}$ is stable in aqueous solution but in the presence of complexing reagents it is easily oxidised.
$(iii)$ The $d^{1}$ configuration is very unstable in ions.