Find the oxidation state, type of hybridization and geometry of the following complex:

${\left[\mathrm{Ni}{\left(\mathrm{CN}\right)}_4\right]}^{2-}$

Find the oxidation state, type of hybridization and geometry of the following complex:

Give the oxidation state, $\mathrm{d}-$orbital occupation and coordination of the central metal atom in the following complex:

${\mathrm{K}}_3\left[\mathrm{Co}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3\right]$