Mortal sins have a different connotation in catholicism, so I'll keep calling them moral sins instead, aka things that she immoral. Moral sins are things that hurt us and others. Jesus died to take the punishment for our sin on himself instead of us. But since moral sin still hurts us and others, we still shouldn't do it. But when we do, we have forgiveness in Christ so that we don't despair about our relationship with God.

Yes the ceremonial laws no longer apply, since we are not in old Israel. Even before Jesus' time, the ceremonial laws concerning the Tabernacle didn't apply. After Jesus, the rest were repealed.