Identify $R$ in the following sequence of reaction:

Which of the following substances will have the lowest boiling point?

When chloroform reacts with ethyl amine in the presence of alcoholic $KOH$,the compound formed is

Given below are two statements:
Statement $I$: Benzenediazonium salt is prepared by the reaction of aniline with nitrous acid at $273-278 \ K$. It decomposes easily in the dry state.
Statement $II$: Insertion of iodine into the benzene ring is difficult and hence iodobenzene is prepared through the reaction of benzenediazonium salt with $KI$. In the light of the above statements,choose the most appropriate answer from the options given below:

The correct structures of $A$ and $B$ formed in the following reactions are:

What is the correct decreasing order of basic strength?