$CO_2$ on reaction with ethyl magnesium bromide gives

Identify the compound $(B)$ in the given reaction.
$CH_3Cl$ $\xrightarrow{KCN} (A)$ $\xrightarrow{H^+ / H_2O} (B)$

An alkyl bromide $X$ $(C_5H_{11}Br)$ undergoes hydrolysis in a two-step mechanism. $X$ is converted to a Grignard reagent and then reacted with $CO_2$ in dry ether followed by acidification to give $Y$. What is $Y$?

When $methyl \ cyanide$ is hydrolysed in the presence of an alkali,the final product is:

What is the product of the following reaction?
$Hex-3-ynal$ $\xrightarrow[(ii) PBr_3]{(i) NaBH_4}$ $\xrightarrow[(ii) CO_2 / H_3O^{+}]{(i) Mg / ether}$ ?

$A$ methyl group attached to a benzene ring can be oxidized to a carboxyl group by reacting with: