The correct statements from the following are: A. The strength of...

The strength of ligands discussed in spectrochemical series.

According to the limitations of VBT,

It does not give a quantitative interpretation of the thermodynamic or kinetic stabilities of coordination compounds.

 Hybridisation of $[ Ni ( CN{)}_{4} ] {}^{- 2}$ is ${dsp}^{2}$.

The outer electronic configuration of ${Ni}^{2 +}$ ion is $3{d}^{8}4{s}^{0}$.

It is a square planar complex. Cyanide ion is a strong field ligand, thus all electrons will be paired.

One $3d$, one $4s$ and two $4p$orbitals undergo ${dsp}^{2}$ hybridization, four equivalent ${dsp}^{2}$ hybrid orbitals which are occupied by $4$ electron pairs of $4$ cyanide ligands.

This forms $[ Ni ( CN{)}_{4} ] {}^{- 2}$

$cis - [ {PtCl}_{2} ( en{)}_{2} ] {}^{2 +}$ complex exhibits optical isomerism, hence, it has two isomers.

Hence statement B and C are correct.