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

Among $TiF_6^{2-}$,$CoF_6^{3-}$,$Cu_2Cl_2$ and $NiCl_4^{2-}$,the colourless species are:

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ The spin only magnetic moment value for $[Fe(CN)_6]^{3-}$ is $1.74 \ BM$,whereas for $[Fe(H_2O)_6]^{3+}$ is $5.92 \ BM$.
Reason $R:$ In both complexes,$Fe$ is present in $+3$ oxidation state.
In the light of the above statements,choose the correct answer from the options given below:

Explain the magnetic properties of coordination compounds.

Which of the following ligands can show linkage isomerism?

Which complex is likely to show optical activity?