For making a distinction between $2$-pentanone and $3$-pentanone, the reagent to be employed is

The product of the reaction is:

Two aliphatic aldehydes $P$ and $Q$ react in the presence of aqueous $K_2CO_3$ to give compound $R$,which upon treatment with $HCN$ provides compound $S$. On acidification and heating,$S$ gives the product shown below:
$1.$ The compounds $P$ and $Q$ respectively are:
$2.$ The compound $R$ is:
$3.$ The compound $S$ is:
Give the answer for questions $1$,$2$ and $3$.

Which of the following observations is found in the Tollens' test for aldehydes?

The final product $A$ in the following reaction sequence is:

The product$(s)$ formed when $m$-chlorobenzaldehyde is heated with concentrated $NaOH$ is/are: