Which of the following acids on heating gives geometrical isomers as a product?

Selected bond angles for six hydrocarbons are shown below. Arrange these hydrocarbons according to their $pK_a$ values,from the lowest to the highest.

Find out the statements which are not true.
$A$. Resonating structure with more number of covalent bonds and lesser charge separation are more stable.
$B$. In electromeric effect, an unsaturated system shows $+E$ effect with nucleophile and $-E$ effect with electrophile.
$C$. Inductive effect is responsible for high melting point, boiling point and dipole moment of polar compounds.
$D$. The greater the number of alkyl groups attached to the doubly bonded carbon atoms, higher is the heat of hydrogenation.
$E$. Stability of carbanion increases with the increase in $s$-character of the carbon carrying the negative charge.
Choose the correct answer from the options given below.

The compounds $(X)$ and $(Y)$ are formed by replacing $H_a$ with $D$ (while keeping $H_b$ as $H$) and replacing $H_b$ with $D$ (while keeping $H_a$ as $H$) respectively in the given molecule. What is the relationship between $(X)$ and $(Y)$?

The possible number of stereoisomers of the product of the following reaction would be: $Ph - CH = CH - CH(CH_3) - CHO \xrightarrow[pH = 4.5]{H_2N - OH}$ ?

Provide the classification of isomerism in alkenes with examples.