What happens when $CCl_4$ is treated with $AgNO_3$?

Which of the following nucleophiles will show minimum reactivity towards $S_N2$ reaction:

$ \xrightarrow[Acetone]{NaI} \underset{(Major)}{X} $ $ \xrightarrow[{S_N2}]{aq. KOH} \underset{(Major)}{Y} $
$X$ and $Y$ should be

Which of the following has the highest reactivity for $S_N2$ reactions?

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

Which of the following reagents,when heated with ethyl chloride,forms ethylene?