Which of the comparison regarding $Zn,\,Cd,\,Hg$ is/are incorrect ?

$(I)$ $ZnCl_2$ is ionic whereas $CdCl_2$ and $HgCl_2$ are covalent

$(II)$ $Zn$ and $Cd$ dissolves in dilute acid $(HCl)$ liberating $H_2$ but $Hg$ can not

$(III)$ $Zn$ and $Cd$ forming with ppt. of $Zn(OH)_2$ and $Cd(OH)_2$ but $Hg$ forms coloured ppt. of

$(IV)$ all from $A_2^{2+}$ type ion

The ability to form complex compounds by the transitional metal ion is due to

Choose the correct statement regarding transition elements?

Identify incorrect statement

Consider the following reaction

$\mathrm{MnO}_2+\mathrm{KOH}+\mathrm{O}_2 \rightarrow \mathrm{A}+\mathrm{H}_2 \mathrm{O} .$

Product ' $A$ ' in neutral or acidic medium disproportionate to give products ' $\mathrm{B}$ ' and ' $\mathrm{C}$ ' along with water. The sum of spin-only magnetic moment values of $B$ and $C$ is . . . . . .$BM$. (nearest integer)

(Given atomic number of $\mathrm{Mn}$ is $25$ )

Besides $Zn$ and $Cu$, german silver contains the metal