Which of the following compounds is most reactive in $S_N 1$ reaction?

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

Which of the following potential energy $(PE)$ diagrams represents the $S_N^1$ reaction?

Which of the following gives the highest yield of $2$-pentene upon reaction with $C_2H_5ONa/C_2H_5OH$?

For the following reactions,which of the following statements is correct?
$A. \, CH_3CH_2CH_2Br + KOH \rightarrow CH_3CH=CH_2 + KBr + H_2O$
$B. \, (CH_3)_2CHBr + KOH \rightarrow (CH_3)_2CHOH + KBr$
$C. \, C_6H_{10} + Br_2 \rightarrow C_6H_{10}Br_2$

What will be the product in the following reaction?
$1$-chloro-$1$-methylcyclohexane $\xrightarrow{H_2O}$ ?