Oxidising nature of H2O2 means it oxidises other substance and itself gets reduced. In such reactions O2 is not evolved.
In (a), MnO4− gets reduced from Mn7+ to Mn2+.
In (b), Fe3+ gets reduced to Fe2+.
In (c), I− gets oxidised to I2.
In (d), KIO4 gets reduced from I7+ to I5+ .