Which of the following complex compounds exhibits geometrical isomerism?

The spin-only magnetic moment of $Fe^{2+}$ ion (in $BM$) is approximately

Total number of stereoisomers of $[Co(acac)_2BrCl]^{\ominus}$ are

In the coordination compound $[Co(en)_2Cl_2]Cl$,which of the following statements is false?

In an experiment,$m$ grams of a compound $X$ (gas/liquid/solid) taken in a container is loaded in a balance as shown in figure $I$ below. In the presence of a magnetic field,the pan with $X$ is either deflected upwards (figure $II$),or deflected downwards (figure $III$),depending on the compound $X$. Identify the correct statement$(s)$:
$(A)$ If $X$ is $H_2O_{(l)}$,deflection of the pan is upwards.
$(B)$ If $X$ is $K_4[Fe(CN)_6]_{(s)}$,deflection of the pan is upwards.
$(C)$ If $X$ is $O_{2(g)}$,deflection of the pan is downwards.
$(D)$ If $X$ is $C_6H_{6(l)}$,deflection of the pan is downwards.

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