Which of the following complexes will exhibit optical isomerism?

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

The complex that can show $fac-$ and $mer-$isomers is

Consider the following complex ions $P = [FeF_6]^{3-}$,$Q = [V(H_2O)_6]^{2+}$,$R = [Fe(H_2O)_6]^{2+}$. The correct order of the complex ions,according to their spin-only magnetic moment values (in $B.M.$) is:

The complexes $[Co(NH_3)_6][Cr(CN)_6]$ and $[Cr(NH_3)_6][Co(CN)_6]$ are the examples of which type of isomerism?

Which of the following complexes is an example of the $MA_2BC$ type of stereoisomers?