Which of the following coordination compounds acts as a non-electrolyte in solution?

$A$ first row transition metal $(M)$ does not liberate $H_{2}$ gas from dilute $HCl$. $1 \ mol$ of aqueous solution of $MSO_{4}$ is treated with excess of aqueous $KCN$ and then $H_{2}S_{(g)}$ is passed through the solution. The amount of $MS$ (metal sulphide) formed from the above reaction is . . . . . . $mol$.

The most stable ion is

Which complex is most stable? Where $k_d =$ Dissociation constant.

Given below are two statements:
Statement $I$ : $N(CH_3)_3$ and $P(CH_3)_3$ can act as ligands to form transition metal complexes.
Statement $II$: As $N$ and $P$ are from same group,the nature of bonding of $N(CH_3)_3$ and $P(CH_3)_3$ is always same with transition metals.
In the light of the above statements,choose the most appropriate answer from the options given below:

$A$ solution containing $2.675 \ g$ of $CoCl_3 \cdot 6 NH_3$ (molar mass $= 267.5 \ g \ mol^{-1}$) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of $AgNO_3$ to give $4.78 \ g$ of $AgCl$ (molar mass $= 143.5 \ g \ mol^{-1}$). The formula of the complex is
(At. mass of $Ag = 108 \ u$)