How many geometrical isomers are possible for the complex $[Mab(AB)_2]^{n \pm}$?

The $[Sc(H_2O)_6]^{3+}$ ion is:

Which of the following complexes is diamagnetic?

The correct order of the calculated spin-only magnetic moments of complexes $A$ to $D$ is:
$A$. $Ni(CO)_{4}$
$B$. $[Ni(H_{2}O)_{6}]Cl_{2}$
$C$. $Na_{2}[Ni(CN)_{4}]$
$D$. $PdCl_{2}(PPh_{3})_{2}$

Magnetic moment $2.83 \ BM$ is given by which of the following ions?
(At. nos. $Ti = 22, Cr = 24, Mn = 25, Ni = 28$)

Which of the following pairs of isomers and their types of isomerism are correct? Select the correct option.
$(1)\ [Co(NH_3)_5(NO_2)]Cl_2$ and $[Co(NH_3)_5(ONO)]Cl_2$: Linkage isomerism
$(2)\ [Cu(NH_3)_4][PtCl_4]$ and $[Pt(NH_3)_4][CuCl_4]$: Coordination isomerism
$(3)\ [Pt(NH_3)_4Cl_2]Br_2$ and $[Pt(NH_3)_4Br_2]Cl_2$: Ionization isomerism