Which of the following statements is incorrect?
(Given that: cycloheptatriene is abbreviated as ‘cht’ and the complexes $\left[Ni{\left(CO\right)}_3\left(cht\right)\right], \left[Ni{\left(CO\right)}_2\left(cht\right)\right]$ and $\left[Cr{\left(CO\right)}_3\left(cht\right)\right]$ follow 18 electron rule)

For the complexes ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$ and ${\left[Fe{\left(CN\right)}_6\right]}^{4-},$ the $\text{C}–\text{N}$ stretching  bands(in $c{m}^{-1}$ ) (corresponding to the highest energy) observed as ${\left[Fe{\left(CN\right)}_6\right]}^{3-}>{\left[Fe{\left(CN\right)}_6\right]}^{4-}$

‘cht’ ligand behaves as two electron donor, four electron donor and six electron donor respectively in $\left[Ni{\left(CO\right)}_3\left(cht\right)\right], \left[Ni{\left(CO\right)}_2\left(cht\right)\right]$ and $\left[Cr{\left(CO\right)}_3\left(cht\right)\right]$ complexes.

cis and trans isomers of the complex $CoC{l}_3.4N{H}_3$ have green and violet colours respectively.

In $CoC{l}_3.6N{H}_3,$ the primary valence of cobalt is satisfied by three $C{l}^{-}$ ions where  as in $CoC{l}_3.4N{H}_3,$ two $C{l}^{-}$ ions satisfy both primary and secondary valences of cobalt.