Which of the following compounds may show optical activity?

Which one of the following has an optical isomer?
$(en = \text{ethylenediamine})$

The value of 'spin only' magnetic moment for one of the following configurations is $2.84 \ BM$. The correct one is:

Select the correct code of $TRUE$ and $FALSE$ for the given statements:
$(a)$ Peroxide ion as well as dioxygen molecule both are paramagnetic species.
$(b)$ In the set of isomers,$[Cr(H_2O)_6]Cl_3$ and $[CrCl(H_2O)_5]Cl_2 \cdot H_2O$,both compounds can easily lose water molecules on treatment with conc. $H_2SO_4$.
$(c)$ During the transformation $NO \to NO^+$,bond length decreases and magnetic behavior changes from paramagnetic to diamagnetic.
$(d)$ An ether is more volatile than an alcohol,both having the same molecular formula.

The spin-only magnetic moment value of the square planar complex $[Pt(NH_3)_2 Cl(NH_2 CH_3)] Cl$ is $B.M.$ (Nearest integer). (Given atomic number for $Pt = 78$)

Why do compounds having similar geometry have different magnetic moments?