What is the authenticity of the narration which states that the splitting of the sea for Moses, peace be upon him, was into seven parts for each tribe, compared to the other narration which mentions that it split into only two parts?

Most exegetes have mentioned that the sea parted into twelve paths, corresponding to the number of the tribes of Israel. This has been authentically narrated from Ibn Abbas and is the chosen view of al-Tabari in his Tafsir (definition). The exegetes did not mention that the sea parted into seven paths. The Qur'an focuses on the purposes and lessons of stories, not on minor details that offer no benefit.