Polysubstitution is a major drawback in

Consider the following anions:
$(I)$ $CF_3SO_3^-$
$(II)$ $C_6H_5SO_3^-$
$(III)$ $C_6H_5O^-$
$(IV)$ $CH_3COO^-$
When attached to $sp^3$ hybridized carbon,their leaving group ability in nucleophilic substitution reaction decreases in the order:

Match the following reactants with their corresponding products:
Reactants:
$(A)$ $C_2H_5Cl$,moist $Ag_2O$
$(B)$ $C_2H_5Cl$,ethanolic $AgCN$
$(C)$ $C_2H_5Cl$,ethanolic $AgNO_2$
$(D)$ $C_2H_5Cl$,ethanolic $KOH$
Products:
$(i)$ $CH_3CH_2ONO$
$(ii)$ $C_2H_4$
$(iii)$ $CH_3CH_2OH$
$(iv)$ $CH_3CH_2NC$
Select the correct match:

$50\%$ of the reagent is used for dehydrohalogenation of $6.45 \ g$ $CH_3CH_2Cl$. What will be the weight of the main product obtained (in $g$)? [At. mass of $H$,$C$,and $Cl$ are $1$,$12$,and $35.5 \ g \ mol^{-1}$ respectively]

$R-X + NaNO_2 \to P + NaX$
$R-X + AgNO_2 \to Q + AgX$
$P$ and $Q$ are related as

Iodoform gives a precipitate with $AgNO_3$ on heating,but chloroform does not because ..........