What are the number of geometrical isomers for the octahedral complex ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_2 {\mathrm{Cl}}_4\right]}^{-}$ and both square planar complexes- ${\left[{\mathrm{AuCl}}_2{\mathrm{Br}}_2\right]}^{-}$ and $\left[\mathrm{Pt}\left(\mathrm{en}\right){\mathrm{Cl}}_2\right]$?

Which one of the following will be able to show geometrical isomerism?

(a) $\mathrm{MABCDEF}, {\mathrm{sp}}^3{\mathrm{d}}^2$ hybridisation.

(b) ${\mathrm{MA}}_3{\mathrm{B}}_3, {\mathrm{sp}}^3{\mathrm{d}}^2$ hybridisation.

(c) $\mathrm{M}{\left(\mathrm{AB}\right)}_2, {\mathrm{sp}}^3$ hybridisation.

(d) $\mathrm{M}{\left(\mathrm{AB}\right)}_3, {\mathrm{sp}}^3{\mathrm{d}}^2$ hybridisation.

In which one of the following chelation increases on reacting with $\left(\mathrm{en}\right)$ or $\left(\mathrm{ox}\right)$?

(i) Trans$[\mathrm{Co}{\left(\mathrm{en}\right)}_2{\mathrm{Cl}}_2{]}^{+}$

(ii) Cis${\left[\mathrm{Co}{\left(\mathrm{en}\right)}_2{\mathrm{Cl}}_2\right]}^{+}$

(iii) Cis${\left[\mathrm{Cr}{\left(\mathrm{ox}\right)}_3\right]}^{3-}$

(iv) Trans${\left[\mathrm{Cr}{\left(\mathrm{ox}\right)}_2{\left({\mathrm{NH}}_3\right)}_2\right]}^{-}$

Consider the following arrangement of the octahedral complex ion ${\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\mathrm{Cl}}_2\right]}^{+}$. Which of the following statements is correct? Assume there is positive charge in all the complexes.