Which of the following will react with a halogen acid at the slowest rate?

Which of the following reactions is used for the conversion of alkyl chloride to alkyl iodide?

$A$ chloro compound $A$:
$(i)$ forms aldehydes on ozonolysis followed by hydrolysis.
$(ii)$ when vaporized completely,$1.53 \ g$ of $A$ gives $448 \ mL$ of vapour at $STP$.
The number of carbon atoms in a molecule of compound $A$ is ...... .

$1-$chlorobutane on treatment with alcoholic potash forms

Rank the following groups in order of decreasing leaving group ability:
$(i)$ $-OSO_2C_6H_4CH_3$ (tosylate)
(ii) $-OCOCH_3$ (acetate)
(iii) $-OCH_3$ (methoxide)
(iv) $-OSO_2CF_3$ (triflate)

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A)$ : Haloalkanes react with $KCN$ to form alkyl cyanides as a main product while with $AgCN$ they form isocyanide as the main product.
Reason $(R)$ : $KCN$ and $AgCN$ both are highly ionic compounds.
In the light of the above statement,choose the most appropriate answer from the options given below: