Arrange the given words in the sequence in which they occur in the dictionary.
i. Forehead
ii. Forensic
iii. Forest
iv. Foremost

Let's compare the words letter by letter according to alphabetical order:
All words start with "Fore". Let's check the 5th letter onwards:

i. Forehead ⟹ 5th letter is 'h'

ii. Forensic ⟹ 5th letter is 'n'

iii. Forest ⟹ 5th letter is 's'

iv. Foremost ⟹ 5th letter is 'm'

Arranging the 5th letters alphabetically: 'h' < 'm' < 'n' < 's'.
Thus, the correct alphabetical order is:

Forehead (i)

Foremost (iv)

Forensic (ii)

Forest (iii)

The sequential arrangement is i, iv, ii, iii.