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

The major product $P$ of the above reaction is:

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ $R-I$ undergoes $S_N2$ reaction faster than $R-Cl$.
Reason $(R):$ Iodine is a better leaving group because of its large size.
In the light of the above statements,choose the correct answer from the options given below:

Arrange the following in order of $C-Br$ bond strength in a polar solvent. The structures are as follows:
$(I)$ $1$-methylcyclohexa-$2,4$-dienyl bromide
$(II)$ cyclohexa-$2,4$-dienyl bromide
$(III)$ $1$-methylcyclopenta-$2,4$-dienyl bromide
$(IV)$ cyclopenta-$2,4$-dienyl bromide

Which one of the following is the best catalyst for the reaction shown below?
$CH_3(CH_2)_8CH_2Br \xrightarrow[benzene]{KCN} CH_3(CH_2)_8CH_2CN$

The decreasing order of reactivity towards dehydrohalogenation $(E_1)$ reaction of the following compounds is:
$(A)$ $CH_3CH_2CH_2CH_2Cl$
$(B)$ $CH_2=CHCH_2CH_2Cl$
$(C)$ $CH_3CH_2CHClCH_3$
$(D)$ $CH_2=CHCHClCH_3$