When approaching the question of how much the prophets of the Old Testament knew of the Savior’s life, consider Psalm 22. This Psalm was used in the temple (and remember, Isaiah was a temple priest and would have received his call to be a prophet in the temple). Psalm 22 begins, "My God, my God, why hast thou forsaken me?" You will recognize these as words that Jesus spoke from the cross. Usually, when we read these words in the accounts of Christ’s crucifixion in the Gospels, we think that it is the end of the story—that Jesus feels as though He has been completely abandoned and left alone.
However, for the ancient Israelites, the opening lines of many of the Psalms were a lot like the opening lines of our hymns. If someone were to hang on a cross and say, "Come, come ye saints," we would know that "no toil nor labor fear" was next. Even if there was toil and labor that the person was called to endure, there would be a positive feeling because we would know that the next line was, "with the saints we shall dwell." We must consider the totality of the hymn in order to understand what was encompassed by and symbolized by that one, opening line. Christ knew this Psalm and knew how it symbolized Him. Likely, all the prophets knew much of what the Savior would have to endure from this hymn alone.
Terry B. Ball, "Isaiah’s ‘Other’ Servant Songs," in The Gospel of Jesus Christ in the Old Testament, The 38th Annual BYU Sidney B. Sperry Symposium (Provo, UT: Religious Studies Center, Brigham Young University, 2009), 207–218.
Book of Mormon Central, "Can Textual Studies Help Readers Understand the Isaiah Chapters in 2 Nephi? (2 Nephi 11:8)," KnoWhy 39 (February 23, 2016).