What is the product $(X)$ in the reaction $C_6H_5NH_2 + HCl + NaNO_2 \rightarrow (X)$?

Rank the following in decreasing order of their acidic strengths:
$(A)$ Tetrahydrofuran-oxonium ion
$(B)$ Pyrrolidine
$(C)$ Cyclopentanol
$(D)$ $N$-methylpyrrolidinium ion

Starting from propanoic acid,the following reactions were carried out: $CH_3-CH_2-COOH$ $\xrightarrow{SOCl_2} X$ $\xrightarrow{NH_3} Y$ $\xrightarrow{Br_2 + KOH} Z$. What is the compound $Z$?

The correct order of basic strength of Pyrrole,Pyridine,and Piperidine is:

Aniline dissolved in dilute $HCl$ is reacted with sodium nitrite at $0\,^oC$. This solution was added dropwise to a solution containing an equimolar mixture of aniline and phenol in dilute $HCl$. The structure of the major product is

An isocyanide on hydrolysis gives