Can you explain the Adam–God doctrine?
I can certainly explain that it is not offical LDS Doctrine. There is no clear scriptural precedent for the typical understanding of Brigham Young‘s comments. Did he mean something else, or did he mean exactly what he said? We just don’t know.
The reason it is not official LDS Doctrine is because the idea does not meet the criteria for modern revelation to the world. The criteria are as follows:
2. The information must be submitted for acceptance as true revelation from God, in order, to the First Presidency, The Quorum of the Twelve Apostles, The Quorums of the Seventy, to the High Priests of the LDS Church, the Elders of the Church, the Aaronic Priesthood holders of the Church, and ultimately to each and every member individually. The Adam-God theory has never been submitted to this process because of the first condition; it was never claimed as revelation.
This is why the theory is in the Journal of Discourses rather than the Standard Works of the LDS Church. The Journal of Discourses is a valuable record of talks and articles by past church leaders, but none of them have any doctrinal authority on the LDS Church in any way.