Which compound is formed when benzene is boiled with concentrated $HCl$?

How would you convert the following compounds into benzene?
$(i)$ Ethyne
$(ii)$ Ethene
$(iii)$ Hexane

What is the major product of the following reaction?
$1$-ethyl-$4$-methylbenzene $\xrightarrow{KMnO_4 + H^+}$ ?

Identify the meta-directing group from the following.

The reaction sequence is as follows:
$1,4-dibromocyclohex-2-ene$ $\xrightarrow[{2 \, molar \, equivalent}]{{(CH_3)_2NH}} (A)$ $\xrightarrow{{BaO}} (B)$ $\xrightarrow[{ (2 \, molar \, equivalent) }]{{CH_3I}} (C)$ $\xrightarrow{{Ag_2O \, / \, H_2O}} (D) + 2(CH_3)_3N$
Identify the end product $(D)$ in the given sequence.

Describe the addition reactions of benzene with chemical equations.