Which one of the following metal complexes is most stable?

Which of the following properties does the $CN^-$ ion possess: $(i)$ reducing agent,$(ii)$ oxidizing agent,and $(iii)$ complexing agent?

Assign $A, B, C, D$ from the given type of reaction:
$3KCN + Fe(CN)_3 \downarrow \longrightarrow K_3[Fe(CN)_6]$

Which of the following complexes is the most stable: $[Fe(H_2O)_6]^{3+}$,$[Fe(CN)_6]^{3-}$,$[Fe(C_2O_4)_3]^{3-}$,or $[FeCl_6]^{3-}$?

The molar ionic conductance of the octahedral complexes:
$(i)$ $PtCl_4 \cdot 5 NH_3$ $(ii)$ $PtCl_4 \cdot 4 NH_3$ $(iii)$ $PtCl_4 \cdot 3 NH_3$ $(iv)$ $PtCl_4 \cdot 2 NH_3$
Follow the order:

Among the properties $(a)$ reducing,$(b)$ oxidising,$(c)$ complexing,the set of properties shown by $CN^{-}$ ion towards metal species is