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

In the following balanced reaction,
$X\,MnO_4^- + Y\,C_2O_4^{2-} + Z\,H^+ \rightleftharpoons X\,Mn^{2+} + 2Y\,CO_2 + \frac{Z}{2}\,H_2O$
values of $X, Y$ and $Z$ respectively are

Assign $A, B, C, D$ from the given type of reaction.
$NH_4Cl + NaNO_2 \xrightarrow{\Delta} N_2 \uparrow + NaCl + 2H_2O$

One mole of potassium dichromate completely oxidises the following number of moles of ferrous sulphate in acidic medium.

After balancing the reaction $Cu + HNO_3 \rightarrow Cu(NO_3)_2 + NO_2 + H_2O$ in an acidic medium,the number of nitrogen atoms,the number of water molecules,and the net charge on the product side are respectively:

Assign $A, B, C, D$ from the given type of reaction.
$MnSO_4 + Sr(NO_3)_2 \longrightarrow SrSO_4 \downarrow + Mn(NO_3)_2$