The maximum number of $RBr$ isomers producing $2-$methylbutane by the given sequence of reactions is $...........$ $(Consider the structural isomers only)$

Identify the major product of the dehydrohalogenation of $CH_3-CH_2-CH(Br)-CH_3$ using an alcoholic base.

Which among the following compounds has the highest boiling point?

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:

$R-X + NaNO_2 \to P + NaX$
$R-X + AgNO_2 \to Q + AgX$
$P$ and $Q$ are related as

The decreasing order of reactivity towards $S_N 1$ reaction for the following compounds is: