Fusion of MnO2 along with KOH and O2 forms X. Electrolytic oxidation of X yields Y. X undergoes disproportionation reaction in acidic medium to MnO2 and Y. The manganese-containing ions present in W and X, respectively, are Y and Z. Correct statement(s) is(are).

(a) Both Y and Z are coloured and have a tetrahedral shape

(b) In an aqueous acidic solution, Y undergoes a disproportionation reaction to give Z and MnO2

(c) Y is diamagnetic in nature while Z is paramagnetic

(d) In both Y and Z, ?-bonding occurs between p-orbitals of oxygen and d-orbitals of manganese