Which among the following alkyl halides gives more than one product upon dehydrohalogenation?

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:

Give the chemical reactions for the following conversions:
$(1)$ Tertiary butyl alcohol from $1-$bromo$-2-$methylpropane
$(2)$ Ethanol from $1,2-$dibromoethane

Which of the following compounds will not undergo Friedel-Crafts reaction with benzene?

$R - X + NaOH \xrightarrow{} ROH + NaX$
The above reaction is classified as:

What is the primary product of an $S_N1$ reaction on an optically active substance?