I heard about a correspondence course offered through the Vatican that covers the Sacrament and/or Catechism. Do you have any information?
The Congregation for the Clergy authorizes the awarding of Catechetical Diplomas through institutions of higher learning. Courses are often offered by correspondence or “distance learning”.
One reputable source is Catholic Distance University.
Also check the USCCB’s Catholic Distance Learning Programs Available for the Laity.