How many geometrical isomers are possible for the complex $[Mab(AB)_2]^{n \pm}$?

An octahedral complex having molecular composition $Co \cdot 5NH_3 \cdot Cl \cdot SO_4$ has two isomers $A$ and $B$. The solution of $A$ gives a white precipitate with $AgNO_3$ solution and the solution of $B$ gives a white precipitate with $BaCl_2$ solution. The type of isomerism exhibited by the complex is,

The spin-only magnetic moments of $[Mn(CN)_6]^{2-}$ and $[MnBr_4]^{2-}$ in Bohr magnetons,respectively are

Which of the following complex ions is not diamagnetic?

Identify the number of complexes that are optically active:
$[Co(en)_3]^{3+}$; $[Co(NH_3)_4Cl_2]^{+}$; $[CoCl_2(en)_2]^{+}$; $[Co(NH_3)_3(NO_2)_3]$

The magnetic moment of $[NiCl_4]^{2-}$ is .... $B.M.$ (spin-only).