What type of isomerism is exhibited by $[Co(NH_3)_6][Cr(CN)_6]$ and $[Cr(NH_3)_6][Co(CN)_6]$?

Total number of unpaired electrons in the complex ions $[Co(NH_3)_6]^{3+}$ and $[NiCl_4]^{2-}$ is...............

The spin-only magnetic moment of cobalt in $Hg[Co(SCN)_4]$ is....

The 'Spin only' magnetic moment for $[Ni(NH_3)_6]^{2+}$ is $ . . . . . . \times 10^{-1} \ BM$.
(Given: Atomic number of $Ni = 28$)

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

An octahedral complex having molecular composition $Co \cdot 5NH_3 \cdot Cl \cdot SO_4$ has two isomers $A$ and $B$. The solution of $A$ gives a white precipitate with $AgNO_3$ solution and the solution of $B$ gives a white precipitate with $BaCl_2$ solution. The type of isomerism exhibited by the complex is,