Which of the following reactions of $KMnO_4$ occurs in acidic medium?

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

$5H_2O_2 + XClO_2 + 2OH^- \to XCl^- + YO_2 + 6H_2O$
In the above balanced reaction,the reaction is balanced when,

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$4FeCr_2O_4 + 8Na_2CO_3 + 7O_2 \longrightarrow 2Fe_2O_3 + 8Na_2CrO_4 + 8CO_2$

$2 IO_3^- + x I^- + 12 H^+ \rightarrow 6 I_2 + 6 H_2 O$. What is the value of $x$?

For the redox reaction
$MnO_{4}^{-} + C_{2}O_{4}^{2-} + H^{+} \longrightarrow Mn^{2+} + CO_{2} + H_{2}O$
the correct coefficients of the reactants for the balanced equation are
$MnO_{4}^{-} \quad C_{2}O_{4}^{2-} \quad H^{+}$