...Could Michael have ordered to kill Clemenza??
No.
In the first version of the script of GF2 there was no Pentangeli. One of the main plotlines was the conflict between Clemenza and Pentangeli. FFC and Puzo even left some lines in the script which referred to Clemenza.
Tom to Pentangeli: "You were always interested in politics and history. I remember you calling about Hitler back in '33."
("They should have stopped Hitler in Munich.")
