The haloform test is given by which of the following substances?

Which of the following compounds is the least reactive towards nucleophilic addition reactions?

The major product of the following reaction is

Which of the following compounds gives the Iodoform reaction?

The product $(A)$ is:

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....