Which of the following compounds does not exhibit optical isomerism? $(en = \text{ethylenediamine})$

$STATEMENT-1$: The geometrical isomers of the complex $[M(NH_3)_4Cl_2]$ are optically inactive.
$STATEMENT-2$: Both geometrical isomers of the complex $[M(NH_3)_4Cl_2]$ possess a plane of symmetry.

The correct increasing order of spin-only magnetic moment values of the complex ions $[MnBr_{4}]^{2-}$ $(A)$, $[Cu(H_{2}O)_{6}]^{2+}$ $(B)$, $[Ni(CN)_{4}]^{2-}$ $(C)$ and $[Ni(H_{2}O)_{6}]^{2+}$ $(D)$ is:

The one that is not expected to show isomerism is:

Total number of geometrical isomers possible for the complexes $[NiCl_4]^{2-}$,$[CoCl_2(NH_3)_4]^{+}$,$[Co(NH_3)_3(NO_2)_3]$ and $[Co(NH_3)_5Cl]^{2+}$ is

Which of the following has a magnetic moment of $1.73 \, B.M.$?