What is the magnetic moment of $[FeF_6]^{3-}$ (in $BM$)?

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

Maximum number of stereoisomers are possible for the octahedral complex $Mabcdef$ :-

The complex that shows Facial - Meridional isomerism is

Which of the following compounds shows optical isomerism?

The magnetic moment of the complex $[Co(NH_3)_6]^{3+}$ is .....