Which of the following is a redox reaction?

Number of moles of $H^{+}$ ions required by $1 \ mole$ of $MnO_4^{-}$ to oxidise oxalate ion to $CO_2$ is . . . . . .

In the reaction $A^{-n_2} + x e^- \to A^{-n_1}$,the value of $x$ is:

In the reaction
$x BrO_3^- + y Cr^{3+} + z H_2O \to Br_2 + CrO_4^{2-} + H^{+}$
the coefficients $x, y, z$ are

Permanganate $(VII)$ ion,$MnO_4^-$,in basic solution oxidises iodide ion,$I^-$,to produce molecular iodine $(I_2)$ and manganese $(IV)$ oxide $(MnO_2)$. Write a balanced ionic equation to represent this redox reaction.

Calculate the value of $n$ in the given reaction:
$MnO_4^{-} + 8H^{+} + n e^{-} \to Mn^{+2} + 4H_2O$