The formation of butane nitrile is possible in which of the following reactions?

Hydrolysis of an alkyl bromide $X$ $(C_5H_{11}Br)$ follows first-order kinetics. Reaction of $X$ with $Mg$ in dry ether followed by treatment with $D_2O$ gives $Y$. What is $Y$?

Consider the following bromides.
The correct order of $S_N1$ reactivity is

Which compound produces acetaldehyde upon heating with aqueous $KOH$?

The major product of the following reaction is:

$50\%$ 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]