Which will form lactone on treatment with $NaOH$?

Identify $A, B$ and $C$ in the following reactions:
$CH_3 Cl$ $\xrightarrow{KCN} A$ $\xrightarrow{H_3 O^{\oplus}} B$ $\xrightarrow{C_2 H_5 OH / H^{+}, \Delta} C$

Assertion : $\beta$-Keto carboxylic acids lose $CO_2$ when heated at about $370 \ K$.
Reason : An enol is first formed by loss of $CO_2$,but it readily tautomerises to the more stable ketone.

$C_6H_5CH_2MgBr$ $\xrightarrow[\text{(ii) } H_3O^{+}]{\text{(i) } CO_2 / \text{Ether}} \text{'X'}$ $\xrightarrow[\Delta]{NaOH + CaO} \text{'Y'}$
What is the final product in this reaction?

What is the product of the reaction between lactic acid and dilute $H_2SO_4$?

The relative reactivities of acyl compounds towards nucleophilic substitution are in the order of