How many geometrical isomers does $[Pt(NH_3)(Br)(Cl)(Py)]$ have?

The number of possible optical isomers for the complexes $MA_{2}B_{2}$ with $sp^{3}$ and $dsp^{2}$ hybridised metal atom,respectively,is.
Note : $A$ and $B$ are unidentate neutral and unidentate monoanionic ligands,respectively.

Give an example of ionization isomerism.

The $d-$ electron configurations of $Cr^{2+}, Mn^{2+}, Fe^{2+}$ and $Co^{2+}$ are $d^4, d^5, d^6$ and $d^7$ respectively. Which one of the following will exhibit the lowest paramagnetic behaviour? (Atomic no. $Cr = 24, Mn = 25, Fe = 26, Co = 27$).

Identify the correct pair of properties of the $[Co(NH_3)_6]^{3+}$ complex ion.

Among $[Ni(CO)_4]$,$[NiCl_4]^{2-}$,$[Co(NH_3)_4Cl_2]Cl$,$Na_3[CoF_6]$,$Na_2O_2$ and $CsO_2$,the total number of paramagnetic compounds is