The correct statement about base hydrolysis of [Co(py)4Cl2]+ (py = pyridine) is

Concept:-

SN¹CB mechanism:

• Substitution is nucleophilic unimolecular by conjugate base mechanism.
• It explains the substitution pathway of metal-ligand complexes. It's also called ligand exchange/displacement reaction.
• The rate-determining step depends on only one reactant molecule. 

Example:

Mechanism

\(L_{1}\:+M-L\rightarrow L_{1}....M....L\rightarrow L_{1}-M\:+L\)

\([Co(NH_3)_5 Cl]^{2+}\:+\:OH^{-}\rightleftharpoons [Co(NH_3)_{4}NH_{2}Cl]^{+}\:H_2O\)

\([Co(NH_3)_{4}NH_{2}Cl]^{+}\:+\:OH^{-}\xrightarrow[-Cl]{RDS}[Co(NH_3)_{4}(NH_{2})_{2}]^{2+}\:Cl^{-} \)

Explanation:​-

• Rate expression is Rate = k[Co(py)4Cl2]+
• All octahedral complexes proceed via a dissociation mechanism. So here SN1CB is not possible also SN1CB depends upon the acidic proton present in the reactant species.
• intermediate involved in this reaction is [Co(py)4Cl2(OH)]- wrong as the reaction doesn't go through SN2 mechanism. The reaction doesn't depend upon the hydroxide concentration.

​Conclusion:-

Hence  option (2)  is the correct one.