The Diels-Alder reaction will not take place with which of the following reactants?

In the reaction with $HCl$,an alkene reacts in accordance with Markovnikov's rule to give the product $1-$chloro$-1-$methylcyclohexane. The possible alkene is:

Reaction of $Br_2$ on ethylene in the presence of $NaCl$ gives:

Explain the preparation of alkene from alkyl halide via dehydrohalogenation in detail.

$A$ hydrocarbon '$X$' with formula $C_6H_8$ uses two moles of $H_2$ on catalytic hydrogenation of its one mole. On ozonolysis,'$X$' yields two moles of methane dicarbaldehyde (malonaldehyde). The hydrocarbon '$X$' is :

$CH_3-CH=CH_2$ $\xrightarrow{Br_2, hv (\text{low conc.})} \dots$ $\xrightarrow{Mg, \text{Dry ether}} \dots$ $\xrightarrow{CH_3-CO-CH_3, NH_4Cl} \dots$ $\xrightarrow{H^{+}, \Delta} (X)$. The end product $(X)$ of the above reaction is: