Which of the following complexes exhibits both geometrical and optical isomerism?

$A$ metal complex of coordination number six having three different types of ligands $a$,$b$ and $c$ of composition $Ma_2b_2c_2$ can exist in several geometrical isomeric forms; the total number of such isomers is

Identify the diamagnetic complexes among the following complexes $K$ to $P$:
$(K)\ K_3[Fe(CN)_6]$
$(L)\ [Co(NH_3)_6]Cl_3$
$(M)\ Na_3[Co(ox)_3]$
$(N)\ [Ni(H_2O)_6]Cl_2$
$(O)\ K_2[Pt(CN)_4]$
$(P)\ [Zn(H_2O)_6](NO_3)_2$

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 one of the following species does not have a magnetic moment of $1.73 \ BM$ (spin only value)?

Among the following complexes,the one that can exist as facial $(fac)$ and meridional $(mer)$ isomers is