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

Given below are two statements:
Statement $I$ : $N(CH_3)_3$ and $P(CH_3)_3$ can act as ligands to form transition metal complexes.
Statement $II$: As $N$ and $P$ are from same group,the nature of bonding of $N(CH_3)_3$ and $P(CH_3)_3$ is always same with transition metals.
In the light of the above statements,choose the most appropriate answer from the options given below:

In $[Fe(CO)_5]$,the $Fe-C$ bond has

$CuSO_4$ decolourises on addition of $KCN$,the product is

Select the correct statement regarding the $[Ni(DMG)_2]$ complex compound.

What is meant by stability of a coordination compound in solution? State the factors which govern stability of complexes.