How many electrons are involved in the reduction of $KMnO_4$ in a basic medium?

The number of moles of $K_2Cr_2O_7$ reduced by $1 \, mol$ of $Sn^{2+}$ is:

In acidic medium,iodide $(I^{-})$ is oxidized to iodine $(I_2)$ by $KMnO_4$. What is the change in the oxidation number of manganese in this reaction?

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

Assign $A, B, C, D$ from the given types of reactions:
$A$: Disproportionation reaction.
$B$: Comproportionation reaction.
$C$: Either intermolecular redox reaction or displacement reaction.
$D$: Either thermal combination redox reaction or thermal decomposition redox reaction.
Reaction: $MnO_4^- + H^+ + Br^- \longrightarrow Mn^{2+}(aq.) + Br_2 \uparrow$

Assign $A, B, C, D$ from the given type of reaction for the following chemical equation:
$3Fe_{(s)} + 4H_2O_{(g)} \xrightarrow{\Delta} Fe_3O_{4(s)} + 4H_{2(g)}$