How early was this sacrificial system known?

Answer

"By faith Abel offered unto God a more excellent sacrifice than Cain, by which he obtained witness that he
was righteous, God testifying of his gifts." Heb. 11: 4. See Gen. 4: 3-5; 8: 20.

How was Christ's first advent to be heralded?
What is required besides a belief in the existence of God?
What saved the people from the predicted overthrow?
With what words did God admonish Cain?
19. What testimony does Eusebius (AD. 270-338), a noted bishop of the church, a flatterer of Constantine, and the reputed father of ecclesiastical history, bear upon this subject?
Seeking a fair remuneration, what do many laborers do?
How does God anticipate the needs of His children?

Questions & Answers are from the book Bible Readings for the Home Circle