Fellow Jews: Please respond to this multi-part question answering each with Torah rationale to support?

EDIT: The original "paschal" lamb was slaughtered, and its blood used to mark the doorposts of those who believed in HaShem, on the night when the first-born of the Egyptians were slain. It represents a sign of faith, not of sinning/repentance/forgiveness. Is that the point you hoped someone would make?