Which of the following exhibits the maximum oxidation state of vanadium?

On heating $Mn(OH)_2$ with $PbO_2$ and conc. $HNO_3$,a pink colour is obtained due to the formation of:

Determine the correct $(T)$ and incorrect $(F)$ statements from the following:
$(a)$ In the titration of $C_2O_4^{2-}$ with $KMnO_4$,$C_2O_4^{2-}$ acts as an oxidizing agent.
$(b)$ $KMnO_4$ is a strong oxidizing agent.
$(c)$ In $Cr_2O_4^{2-}$,the $O-Cr-O$ bond angle is $120^o$.
$(d)$ The standard electrode potential for the reaction $Cr_2O_7^{2-} + 14H^+ + 6e^- \to 2Cr^{3+} + 7H_2O$ is $E^o = -1.33 \ V$.

Select the salt whose aqueous solution is not green.

Excess of $KI$ reacts with $CuSO_4$ solution and then $Na_2S_2O_3$ solution is added to it. Which of the statements is incorrect for this reaction?

Amphoteric oxide$(s)$ of $Mn$ is/are: