Which 'off' is used as a preposition?

Preposition -- The island is just off the coast of Florida. (Off = near to)
Verb -- They offed him and dumped his body in the swamp. (Off = to kill someone)
Adjective -- How are you off for money? (Off = having a particular amount or number, especially of money)
Adverb -- The good thing about exercise is that it burns off calories. (Off = in such a way as to be completely absent, especially because of having been used or killed)

Source: Cambridge Dictionary.