Which among the following reactions does not occur?

How many of the four monochloro derivatives of $(CH_3)_2CHCH_2CH_3$ are optically active?

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:

Correct reactivity order of alkyl halide towards dehydrohalogenation-

The reaction $CH_3-CH(C_6H_5)-CH(Br)-C_6H_5 \xrightarrow{alc.KOH} A$. Identify the product $A$.

The compound added to prevent chloroform from forming phosgene gas is