The Seventh Imam!!!! The Twelvers are totally wrong.
The seventh Imam thing is a totaly different sec. It's part of a Shia cult spin off which developed in the 12th century.
Most of Islams basic religion is found in Ishaqs hadith,which is the oldest and ONLY record of Muhammads life and sayings. It's preserved (and bad stuff edited out) by the writtings of Tabari and Hisham, and further edited years later by Bukhari and his student, Muslim. All other, more modern writings are edited, modified, abrogated etc.