Which of the following complexes will show both geometrical and optical isomerism?

Which of the following compounds has the highest magnetic moment?

Of the following configurations,the optical isomers are

Choose the correct code regarding the possible number of geometrical isomers exhibited by the following complexes:
$I. [CrCl_2(NO_2)_2(NH_3)_2]^-$
$II. [Co(NO_2)_3(NH_3)_3]$
$III. [PtCl(NO_2)(NH_3)(py)]$
$IV. [PtBrCl(en)]$
Select the correct sequence for $I - II - III - IV$.

In $Cr^{2+}, Mn^{2+}, Fe^{2+},$ and $Ni^{2+}$,the number of electrons in the $3d$ orbital are $3d^4, 3d^5, 3d^6,$ and $3d^8$ respectively. Which of the following aqueous complexes will have the lowest magnetic moment?

Select the correct statement about the given square planar complex.