If Containment Breach resolves, and the target artifact has a mana value of 2 or less, but it wasn't destroyed (perhaps because it has indestructible), you will still create a Pest.

If the artifact or enchantment is an illegal target as Containment Breach tries to resolve, it won't resolve and none of its effects will happen. You won't create a Pest.

Lesson is a spell subtype found on some instant and sorcery cards in the Strixhaven set. The Lesson subtype has no special rules associated with it.

Although you may want to include Lessons in your sideboard if you're playing with cards that instruct you to learn, Lesson cards can be included in your main deck like other instant or sorcery cards.