What is formed when benzaldehyde reacts with chlorine in the absence of a catalyst?

The end product $(C)$ in the following reaction is:

Identify the product formed in the following reaction: $CH_3-CH=CH-CH_2-CHO \xrightarrow[(ii) \ H_3O^{+}]{(i) \ LiAlH_4} \text{Product}$

Complete reaction of acetaldehyde with excess formaldehyde,upon heating with conc. $NaOH$ solution,gives $P$ and $Q$. Compound $P$ does not give Tollens' test,whereas $Q$ on acidification gives positive Tollens' test. Treatment of $P$ with excess cyclohexanone in the presence of catalytic amount of $p$-toluenesulfonic acid $(PTSA)$ gives product $R$. Sum of the number of methylene groups $(-CH_2-)$ and oxygen atoms in $R$ is....

For the sequence of reactions $A$ $\xrightarrow{C_2H_5MgI} B$ $\xrightarrow{H_2O / H^{+}} \text{tert-pentyl alcohol}$. The compound $A$ in the sequence is

The reagent with which both acetaldehyde and acetone react is