Which of the following reactions are disproportionation reactions?...

In disproportionation reaction,  both oxidation and reduction of same chemical species occurs.

• Oxidation is gain in oxidation number.
• Reduction is loss in oxidation number.

$1 ){Cu}^{+} ⟶ {Cu}^{2 +} + Cu$

Oxidation state of ${Cu}^{+} = + 1$.

Oxidation state of ${Cu}^{2 +} = + 2$.

Oxidation state of $Cu = 0$ .

Here, ${Cu}^{+}$ is getting both reduced and oxidised.

$2 )3{MnO}_{4}^{-} + 4H^{+} ⟶ 2{MnO}_{4}^{-} + {MnO}_{2} + 2{H}_{2}O$

Oxidation state of $Mn$ in ${MnO₄}^{-} = + 7$.

Oxidation state of $Mn$ in ${MnO}_{2} = + 4$.

Here, reduction is taking place.

$3 )2{KMnO}_{4} ⟶ {K}_{2}{MnO}_{4} + {MnO}_{2} + {O}_{2}$

Here in the reaction, $Mn$ is changing its oxidation state from $+ 7$ to $+ 6$and $+ 4$. In both cases, reduction is occurring.

$4 )2{MnO}_{4}^{-} + 3{Mn}^{2 +} + 2{H}_{2}O ⟶ 5{MnO}_{2} + 4H^{+}$

Here in the reaction, product with $Mn$ in only one, so there is no possibility of both oxidation and reduction reactions at the same time.