you wrote: “Please show where “the teaching” included the assumption of Mary and the requirement to believe it.”
I posted a link to that teaching. http://w2.vatican.va/content/pius-xii/en/apost_constitutions/documents/hf_p-xii_apc_19501101_munificentissimus-deus.html
Deny it all you want, but there it is.
Aside from the massive amounts of circular logic shown in the text; this leaped out at me:
6. Thus, when it was solemnly proclaimed that Mary, the Virgin Mother of God, was from the very beginning free from the taint of original sin, the minds of the faithful were filled with a stronger hope that the day might soon come when the dogma of the Virgin Mary's bodily Assumption into heaven would also be defined by the Church's supreme teaching authority.Stronger HOPE?
Most readers would understand that "the teaching" was referring to what the apostles taught.