Which of the following can show optical isomerism?

Amongst $TiF_6^{2-}$,$CoF_6^{3-}$,$Cu_2Cl_2$,and $NiCl_4^{2-}$ (Atomic numbers: $Ti=22, Co=27, Cu=29, Ni=28$),the colourless species are:

Which of the following complex compounds is optically inactive?

The calculated spin-only magnetic moment values in $BM$ for $[FeCl_4]^-$ and $[Fe(CN)_6]^{3-}$ are

Which of the following complex ions does not absorb visible light?

The pair$(s)$ of coordination complexes/ions exhibiting the same kind of isomerism is(are)
$(A)$ $[Cr(NH_3)_5Cl]Cl_2$ and $[Cr(NH_3)_4Cl_2]Cl$
$(B)$ $[Co(NH_3)_4Cl_2]^+$ and $[Pt(NH_3)_2(H_2O)Cl]^+$
$(C)$ $[CoBr_2Cl_2]^{2-}$ and $[PtBr_2Cl_2]^{2-}$
$(D)$ $[Pt(NH_3)_3(NO_3)]Cl$ and $[Pt(NH_3)_3Cl]Br$