Which one of the following compounds will be most reactive for $S_N1$ reactions?

Consider the following $E_1/S_N1$ reaction. The missing product$(s)$ is(are):

Write the structure of the major organic product in each of the following reactions:
$(i)$ $CH_3-CH_2-CH_2-Cl + NaI \xrightarrow[\text{heat}]{\text{acetone}}$
$(ii)$ $CH_3-C(CH_3)_2-Br + KOH \xrightarrow[\text{heat}]{\text{ethanol}}$
$(iii)$ $CH_3-CH(Br)-CH_2-CH_3 + NaOH \xrightarrow{\text{water}}$
$(iv)$ $CH_3-CH_2-Br + KCN \xrightarrow{\text{aq. ethanol}}$
$(v)$ $C_6H_5-ONa + C_2H_5-Cl \longrightarrow$
$(vi)$ $CH_3-CH_2-CH_2-OH + SOCl_2 \longrightarrow$
$(vii)$ $CH_3-CH_2-CH=CH_2 + HBr \xrightarrow{\text{peroxide}}$
$(viii)$ $CH_3-CH=C(CH_3)_2 + HBr \longrightarrow$

Rank the following compounds in order of decreasing rate of $E_2$ reaction.

Identify the correct order of reactivity for the following pairs towards the respective mechanism:
$(A)$ $S_{N}2$: Isobutyl bromide > tert-Butyl bromide
$(B)$ $S_{N}1$: Benzyl bromide > $2-$Phenylethyl bromide
$(C)$ Electrophilic substitution: Chlorobenzene > $1-$Chloro$-4-$nitrobenzene
$(D)$ Nucleophilic substitution: Bromobenzene < $1-$Bromo$-4-$nitrobenzene
Choose the correct answer from the options given below:

Consider the reaction sequence: Alkyl halide $\xrightarrow[\text{Ether}]{Mg}$ Grignard Reagent $\xrightarrow{H_2O}$ Propane. The alkyl halide can be: