Which of the following exhibits optical isomerism? $(en = \text{ethylenediamine})$

Which of the following complex species is not expected to exhibit optical isomerism?

Which of the following has diamagnetic character?

Number of paramagnetic complexes among the following is . . . . . . . $[MnBr_4]^{2-}$,$[NiCl_4]^{2-}$,$[Ni(CN)_4]^{2-}$,$[Ni(CO)_4]$,$[CoF_6]^{3-}$,$[Fe(CN)_6]^{4-}$,$[Mn(CN)_6]^{3-}$,$[Ti(CN)_6]^{3-}$,$[Cu(H_2O)_6]^{2+}$,$[Co(C_2O_4)_3]^{3-}$

$(a) \ CoCl_{3} \cdot 4 NH_{3}$
$(b) \ CoCl_{3} \cdot 5 NH_{3}$
$(c) \ CoCl_{3} \cdot 6 NH_{3}$
$(d) \ CoCl(NO_{3})_{2} \cdot 5 NH_{3}$
Number of complex(es) which will exist in $cis-trans$ isomerism is/are ....

How many geometrical isomers and stereoisomers are possible for $[Pt(NO_2)(NH_3)(NH_2OH)(Py)]^+$ and $[Pt(Br)(Cl)(I)(NO_2)(NH_3)(Py)]$ respectively?