Which of the following reactions involves both oxidation and reduction?

In the titration of $KMnO_{4}$ and oxalic acid in acidic medium,the change in oxidation number of carbon at the end point is

$KMnO_4$ reacts with ferrous sulphate according to the equation:
$MnO_4^- + 5Fe^{2+} + 8H^{+} \to Mn^{2+} + 5Fe^{3+} + 4H_2O$
Here,$10 \ mL$ of $0.1 \ M$ $KMnO_4$ is equivalent to:

Balance the following redox reactions using the oxidation number and ion-electron method:
$(1) H_2S + Fe^{3+} \to Fe^{2+} + S + H^{+}$
$(2) Cu + NO_3^{-} \to Cu^{2+} + NO_2$
$(3) Sn + NO_3^{-} + H^{+} \to Sn^{2+} + NH_4^{+} + H_2O$
$(4) As + NO_3^{-} + H^{+} \to AsO_4^{3-} + NO_2 + H_2O$

How many moles of $KMnO_4$ will be reduced by $1$ mole of $KI$ in an alkaline medium?

In the given reaction,calculate the number of electrons lost by iron:
$3Fe + 4H_2O \to Fe_3O_4 + 4H_2$