What is added to chloroform to prevent it from becoming toxic when used as an anesthetic?

Choose the false statement from the following about $S_N1$ reaction mechanism.

For each of the following pairs of $E_2$ reactions,select the one that occurs with the greater rate constant:
$(1)$ $CH_3-CH_2-CH_2-Cl + CH_3-C(CH_3)_2-O^-$
$(2)$ $CH_3-CH_2-CH_2-I + CH_3-C(CH_3)_2-O^-$
$(3)$ $CH_3-CH(Br)-CH_3 + CH_3-O^-$
$(4)$ $CH_3-CH(Br)-CH_3 + CH_3-S^-$
$(5)$ $Ph-CH_2-CH(Br)-CH_2-CH_3 + OH^-$
$(6)$ $Ph-CH_2-CH_2-CH(Br)-CH_3 + OH^-$

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

Benzene hexachloride is

The major product in the given reaction is: