Two words have identical sound and spelling, but not related in meaning. It is known as—

Homonymy refers to the phenomenon where two words have the same spelling AND same pronunciation but unrelated meanings (e.g., 'bat' the animal vs. 'bat' the cricket equipment). Homophones share sound but not necessarily spelling. Homographs share spelling but not necessarily pronunciation. Polysemy involves related meanings. Since the question specifies identical sound AND spelling with unrelated meanings, this is homonymy. Hence (2) is correct.