Christianity vs. Mormonism (Part 3)

Can God Lie?

1. Mormonism: In Joseph Smith's Pearl of Great Price , Abraham and wife Sarah are on their way to Egypt when the Lord tells Abraham the Egyptians will find beauty in his wife and tells him to lie and say she is his sister in order to save his life.
1. "Let her say unto the Egyptians, she is thy sister, and thy shall live." - Book of Abraham 2:24

2. The Bible: We find a very similar story in Genesis 20, only it is Abraham who lied about Sarah being his sister. Abraham told this lie on his own; this was not a command by God.
1. "You shall not bear false witness." - Exodus 20:16
2. "All liars shall have their part in the lake which burns with fire and brimstone…" - Revelation 21:8
3. "in hope of eternal life which God, who cannot lie, promised before time began" - Titus 1:2
4. "that by two immutable things, in which it is impossible for God to lie, we might have strong consolation, who have fled for refuge to lay hold of the hope set before us. - Hebrews 6:18

How do we know?

So how do we know the true answer? Is there one God or millions of gods? Why would God give us the Bible for instruction and life molding and later give us another testament of Jesus Christ only to contradict each other. Does God make mistakes? Why the Bible AND the Book of Mormon?