How is the $t_{2g}^4 e_g^0$ configuration possible for a $d^4$ ion during crystal field splitting in an octahedral complex?

Correct increasing order for the wavelength of absorption in the visible region for the complexes of $Co^{3+}$ is :

The configurations of the complexes of manganese $A$ and $B$ respectively are $t_{2g}^3 e_g^1$ and $t_{2g}^4 e_g^0$. Then $A$ and $B$ are:

Given below are two statements:
Statement $I$: Presence of a large number of unpaired electrons in transition metal atoms results in higher enthalpies of their atomisation.
Statement $II$: $d_{xy} = d_{xz} = d_{yz} < d_{x^2-y^2} = d_{z^2}$ and $d_{x^2-y^2} < d_{xy} = d_{xz} = d_{yz}$ are the $d$-orbital splittings in $[Fe(H_2O)_6]^{3+}$ and $[Ni(Cl)_4]^{2-}$ complex ions respectively.
In the light of the above statements, choose the correct answer from the options given below:

$[Fe(CN)_{6}]^{4-}$ and $[Fe(H_{2}O)_{6}]^{2+}$ are of different colours in dilute solutions. Why?

Complexes with $CN^-$ ligands are generally...