Regarding the question you have asked, it is a known fact that legislation differs from one Shari'ah to another, while the principles and beliefs remain the same in all of them. So, making of portraits was allowed in the Shari'ah of Sulayman (peace be upon him) but is prohibited in our Shari'ah. Similarly, making prostration of salutation was permitted in the Shari'ah of Yusuf (peace be upon him) but is illegal in ours. Also, war booty was prohibited for nations before us but it is completely legal for us. The Qiblah of people before us used to be towards Bayt Al-Maqdis, but for us it is towards Ka'bah. In a similar way, marriage between brothers and sisters was permitted in the Shari'ah of Adam (peace be upon him) as opposed to those that came afterwards. The following is a clarification on the issue by Haafidh Ibn Katheer, who said:
Allaah allowed Adam (peace be upon him) to marry his daughters to his sons for necessity. Every couple used to have a boy and a girl. Hence, he married the girl of one couple to the boy of another. This is said by Suddi regarding what has been narrated by Abu Maalik and Abu Salih, from Ibn ‘Abbas, by Murrah from Ibn Mas‘ood and by other companions of the Prophet (peace be upon him) that Adam did not have (in his grandchildren) a baby boy unless it was accompanied by a girl, so he married the male of a couple to the female of
(peace be upon him) that Adam did not have (in his grandchildren) a baby boy unless it was accompanied by a girl, so he married the male of a couple to the female of another, and the female of a couple to the male of another...
and allah(swt) knows best, ill try to get more on this..