Authentic Thaumaturgy, Rituals and Avatars

1. Can an Avatar cast Significant rituals if he or she gets a charge? I.E. The Mystic Hermafrodite gets significant charges at high skill levels; and several minor rituals generate Significant charges; do an Avatars roll their skill as with Minor rituals?

2. Adepts can cast the Minor and Significant rituals, but do they need to learn them with XP as Thaumaturges do? The same question for Avatars