Reaction Mechanism Questions

Which of the following is the correct order of decreasing $S_{N}2$ reactivity? ($X=\text{a halogen}$)

The organic chloro compound which shows complete stereochemical inversion during a ${\text{S}}_{N}2$ reaction is:

Consider the reaction:${\text{Cl}}_2(aq)+{\text{H}}_2\text{S}(aq)\to \text{S}(s)+2{\text{H}}^{+}(aq)+2{\text{Cl}}^{-}(aq)$ The rate equation for this reaction is $\text{rate}=k[{\text{Cl}}_2][{\text{H}}_2\text{S}]$.Which of these mechanisms is/are consistent with this rate equation?(A) ${\text{Cl}}_2+{\text{H}}_2\text{S}\to {\text{H}}^{+}+{\text{Cl}}^{-}+{\text{Cl}}^{+}+{\text{HS}}^{-}$ (slow)${\text{Cl}}^{+}+{\text{HS}}^{-}\to {\text{H}}^{+}+{\text{Cl}}^{-}+\text{S}$ (fast)(B) ${\text{H}}_2\text{S}\rightleftharpoons {\text{H}}^{+}+{\text{HS}}^{-}$ (fast equilibrium)${\text{Cl}}_2+{\text{HS}}^{-}\to 2{\text{Cl}}^{-}+{\text{H}}^{+}+\text{S}$ (slow)

Consider the following bromides:

The correct order of ${\text{S}}_{\text{N}}1$ reactivity is:

The main product of the following reaction is
: