What are the drawbacks of valence bond theory in coordination compounds?

Consider the following complex ions, P, Q and R.

$\mathrm{P}={\left[{\mathrm{FeF}}_6\right]}^{3-},\mathrm{Q}={\left[\mathrm{V}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}, \mathrm{R}={\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ 

The correct order of the complex ions, according to their spin-only magnetic moment values (in B.M.) is

For octahedral $\mathrm{Mn}\left(\mathrm{II}\right)$ and tetrahedral $\mathrm{Ni}\left(\mathrm{II}\right)$ complexes, consider the following statements :

$\left(\mathrm{I}\right)$ both the complexes can be high spin.

$\left(\mathrm{II}\right)$ $\mathrm{Ni}\left(\mathrm{II}\right)$ complex can very rarely be of low spin.

$\left(\mathrm{III}\right)$ with strong field ligands, $\mathrm{Mn}\left(\mathrm{II}\right)$ complexes can be low spin.

$\left(\mathrm{IV}\right)$ aqueous solution of $\mathrm{Mn}\left(\mathrm{II}\right) \mathrm{ions}$ is yellow in color.

The correct statements are :