The possible number of stereoisomers for $[Co(en)_2Cl_2]^+$ is

What is the value of the magnetic moment of $Co^{2+}$ (in $BM$)?

Arrange the following complexes in the increasing order of their spin only magnetic moment (in $B.M$):
$I$. $[Fe(CN)_6]^{4-}$
$II$. $[MnCl_4]^{2-}$
$III$. $[Mn(CN)_6]^{4-}$
$IV$. $[Cr(NH_3)_6]^{3+}$

The magnetic moment of $[Fe(H_2O)_6]^{3+}$ is $5.92 \ BM$,whereas the magnetic moment of $[Fe(CN)_6]^{3-}$ is $1.74 \ BM$. Explain why.

Which of the following pairs of isomers and their types of isomerism are correctly matched?
$1.$ $[Co(NH_3)_5NO_2]Cl_2$ and $[Co(NH_3)_5ONO]Cl_2$ $-$ Linkage
$2.$ $[Cu(NH_3)_4] [PtCl_4]$ and $[Pt(NH_3)_4] [CuCl_4]$ $-$ Coordination
$3.$ $[Pt(NH_3)_4Cl_2]Br_2$ and $[Pt(NH_3)_4Br_2]Cl_2$ $-$ Ionization

Which of the following does not exhibit geometrical isomerism?