Alkyl iodides on keeping become dark in color due to ...........

Predict all the alkenes that would be formed by dehydrohalogenation of the following halides with sodium ethoxide in ethanol and identify the major alkene:
$(i)$ $1-$Bromo$-1-$methylcyclohexane
$(ii)$ $2-$Chloro$-2-$methylbutane
$(iii)$ $2,2,3-$Trimethyl$-3-$bromopentane.

Where $Nu =$ Nucleophile. Find out the correct statement from the options given below for the above $2$ reactions.

Increasing order of reactivity of the following compounds for $S_N1$ substitution is:
$(a)$ $(CH_3)_2CH-CH_2Cl$
$(b)$ $CH_3CH_2Cl$
$(c)$ $CH_3O-C_6H_4-CH_2Cl$
$(d)$ $C_6H_5-CH_2Cl$

Which of the following compounds will undergo $E_2$ elimination reaction to give a single product in the presence of a strong base?

What is the product $(B)$ of the following reaction sequence?