Which compound is formed when $H_2S$ gas is passed through an acidic solution of $KMnO_4$?

What is the stoichiometric coefficient of the oxalate ion after balancing the following redox reaction?
$MnO_4^- + C_2O_4^{2-} + H^+ \rightarrow Mn^{2+} + CO_2 + H_2O$

The product of $I^-$ with $MnO_4^-$ in acidic medium is

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

$KMnO_4$ in basic medium is reduced to

Aqueous solutions of $Na_2S_2O_3$ on reaction with $Cl_2$ gives