right hand

Respected scholars, as-salamu `alaykum. Can you please clarify what Islam says about a man wearing a ring on the first finger of the right hand, because I have heard that it is not allowed to do so. Jazakum Allahu Khayran.

Is it true that Islam permits Muslim men to own slave women, and permits them to have sex with them without marrying them? And that this was carried out by the Prophet’s Companions with his approval? Surely, this is in contradiction of the Qur’an's condemnation of zina. Could you please clarify this issue?