What is the ruling on someone who utters polytheistic phrases - which he does not understand - after being ordered by someone to repeat them, and he suspected there was polytheism in them, yet without intending polytheism? And does he incur a legal punishment (hadd) or does he need to repent?

It is not permissible to perform Ruqyah (exorcism/healing through prayer) or supplication using unknown phrases, due to the possibility of them containing polytheism (shirk). The one who does so must repent. In this situation, we hope that it does not amount to disbelief (kufr), because the speaker did not know what he was saying and it was not clear to him that it was shirk. If a non-Arabic speaker or an Arab utters words of disbelief, faith, divorce, or anything else, while not knowing their meaning, he is not held accountable for them, because intention is only directed towards what is known or presumed.