Dear Ignatius:

There three levels of adoration/veneration:

1) Cultus dulia, which is the veneration due to angels and saints.

2) Cultus Hyperdulia, which is the veneration due solely to our Blessed Mother. The reason she is venerated at a higher level is that she is the Mother of God and the Queen of Heaven, both unique positions given to her alone. Thus, she is venerated above all angels and other Saints.

3) Cultus latria, which is the adoration given only to God.

As for the Mediatrix of all Graces:

The Second Vatican Council (Lumen gentium # 61-62), said:

"The Blessed Virgin is invoked in the Church under the titles of Advocate, Auxiliatrix, Adiutrix, and Mediatrix. This however it to be so understood that it takes nothing away, or adds nothing to the dignity and efficacy of Christ the one Mediator. For no creature can ever be put on the same level with the Incarnate Word and Redeemer...."

Since there has not been a dogmatic definition declared, the details as to her mediation of "all graces" or not and other details of the teaching are still being debated.

You can read more about this in the article, Mary, Mediatrix of All Graces by Fr, William Most. Father Most has gone to the Lord, but he was one of the top theologians in the U.S.

God Bless,
Bro. Ignatius Mary