The complexes given below show:

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 complexes or complex ions can have an optically active isomer?

Which of the following complexes does not show optical isomerism?

The isomer$(s)$ of $[Co(NH_{3})_{4}Cl_{2}]^{+}$ that has/have a $Cl-Co-Cl$ angle of $90^{\circ}$ is/are:

$[Co(NH_3)_5NO_2]Cl_2$ and $[Co(NH_3)_5(ONO)]Cl_2$ are related to each other as