I think the 12th imam is what some shit`tes are waiting for. Imanutjob is one of them. They are the ones that believed that the imam job should have went down mohammad’s male line instead of being chosen.
I don’t know that they considered any of those imams as Messiahs just that they consider mohammad as the last Messiah/Prophet. They believe that Jesus was a great Messiah/Prophet but not the Son of God.