The best leaving group is :

${\mathrm{CH}}_3-\stackrel{⊝}{\mathrm{S}}\stackrel{\oplus }{\mathrm{Na}}+{\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{x}⟶$

The reaction is fastest when $\mathrm{X}$ is 

The correct nucleophilicity order is

One of the possible product is :

The rate of Hydrolysis ( ${\mathrm{S}}_{\mathrm{N}}1$ ) reaction for the given molecules is

(iii) $\mathrm{Ph}-{\mathrm{CH}}_2-\mathrm{Cl}$

(iv) ${\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CH}}_2-\mathrm{Cl}$

Which of the following statement/s is/are correct about the mechanism of this reaction?