In an $S_N1$ reaction on chiral centres,there is

$1$-chlorobutane on reaction with alcoholic potash gives

The major product obtained in the following reaction is $C_2H_5ONa + (CH_3)_3C-Cl \rightarrow$

$2-$Methylpropyl bromide reacts with $C_2H_5O^-$ to give $A$,whereas on reaction with $C_2H_5OH$ it gives $B$. The mechanism followed in these reactions and the products $A$ and $B$ respectively are:

Arrange the compounds of each set in order of reactivity towards $S_{N}2$ displacement:
$(i)$ $2-Bromo-2-methylbutane$,$1-Bromopentane$,$2-Bromopentane$
$(ii)$ $1-Bromo-3-methylbutane$,$2-Bromo-2-methylbutane$,$2-Bromo-3-methylbutane$
$(iii)$ $1-Bromobutane$,$1-Bromo-2,2-dimethylpropane$,$1-Bromo-2-methylbutane$,$1-Bromo-3-methylbutane$.

Heating methyl chloride with zinc in a closed tube produces...............