OP1 & OP4 which is better to choose in my case?

@Francisca_Chiedu, I am not too sure about your comment. Another endorsee, @dai-ichi, also used MSc distinction and a letter from an MSc programme leader. Besides, the guidelines do not seem to suggest that an award received during your MSc does not count or that a letter from an MSc supervisor is not appropriate. Of course, it depends on how well your supervisor knows you and the actual content of the reference letter.