Identify $\mathrm{X},\mathrm{Y}$ and $\mathrm{Z}$ in the following synthetic scheme and write their structures.

${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{C}\equiv \mathrm{C}-\mathrm{H}\underset{(\mathrm{ii}) {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Br}}{\overset{ (\mathrm{i}) {\mathrm{NaNH}}_2}{\to }}\mathrm{X}\stackrel{{\mathrm{H}}_2/\mathrm{Pd}.{\mathrm{BaSO}}_4}{⟶}\mathrm{Y}\stackrel{\mathrm{alkaline} {\mathrm{KMnO}}_4}{\to }\mathrm{Z}$

Is the compound $\mathrm{Z}$ optically active? Justify your answer.

The major product in the following reaction is :

The acidic hydrolysis of ether $\left(\mathrm{X}\right)$ shown below is the fastest when :

The major product of the reaction

For the following compounds, the correct statement(s) with respect to nucleophilic substitution reaction is (are)

In the following reaction sequence, the correct structure(s) of $\mathrm{X}$ is (are)