Which of the following compounds is obtained when $Bromoethane$ is reacted with silver acetate?

An alkyl halide $X$ $(C_4H_9Br)$ undergoes nucleophilic substitution by $S_N2$ reaction. The product of $X$ on reaction with $Mg/\text{dry ether}$ followed by $D_2O$ is:

An incorrect statement with respect to $S_N1$ and $S_N2$ mechanisms for alkyl halide is

$KCN$ reacts readily to give a cyanide with:

Compound $(A), \, C_8H_9Br,$ gives a white precipitate when warmed with alcoholic $AgNO_3.$ Oxidation of $(A)$ gives an acid $(B), \, C_8H_6O_4.$ $(B)$ easily forms anhydride on heating. Identify the compound $(A).$

Which one of the following is more readily hydrolysed by $S_{N}1$ mechanism?