Decreasing order towards SN 1 reaction for the following compounds is:

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason $\mathbf{R}$.

Assertion A: Antihistamines do not affect the secretion of acid in stomach.

Reason $\mathbf{R}$ : Antiallergic and antacid drugs work on different receptors.

In the light of the above statements, choose the correct answer from the options given below:

$\mathrm{KMnO}_4$ oxidises $\mathrm{I}^{-}$ in acidic and neutral/faintly alkaline solutions, respectively, to :

In the above conversion of compound $(\mathrm{X})$ to product $(\mathrm{Y})$, the sequence of reagents to be used will be: