Which of the following compounds does $NOT$ undergo Williamson's synthesis?

Which of the following ethers will undergo electrophilic substitution reaction?

Give the major products that are formed by heating each of the following ethers with $HI$.
$(i)$ $CH_3-CH_2-CH(CH_3)-CH_2-O-CH_2-CH_3$
$(ii)$ $CH_3-CH_2-CH_2-O-C(CH_3)_2-CH_2-CH_3$
$(iii)$ $C_6H_5-CH_2-O-C_6H_5$

Acetic anhydride reacts with diethyl ether in the presence of anhydrous $AlCl_3$ to form:

The products formed in the following reaction are $C_6H_5-OCH_3 + HI \xrightarrow{\text{heat}}$

Dimethyl ether when heated with excess $HI$ gives