The possible geometrical isomers of octahedral complex $\mathrm{Mabcdef}$ are 

Number of stereoisomers possible for the octahedral complexes $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_3{\mathrm{Cl}}_3\right]$ and $\left[\mathrm{Ni}(\mathrm{en}{)}_2{\mathrm{Cl}}_2\right],$ respectively, are:

[$\mathrm{en}=1, 2$-ethylenediamine]

The number of stereo isomers possible for ${\left[\mathrm{Co}{\left(\mathrm{ox}\right)}_2\left(\mathrm{Br}\right)\left({\mathrm{NH}}_3\right)\right]}^{2-}$ is __________.

[$\mathrm{ox}=$ oxalate]

Three arrangements are shown for the complex, ${\left[\mathrm{Co}\left(\mathrm{en}\right){\left({\mathrm{NH}}_3\right)}_2{\mathrm{Br}}_2\right]}^{+}.$ Which one is the wrong statement-

Both geometrical and optical isomerisms are shown by

${\left[Pt\left({\mathrm{NH}}_3\right)\left({\mathrm{NO}}_2\right)Py\left({\mathrm{NH}}_2\mathrm{OH}\right)\right]}^{+}$ will form how many geometrical isomers?