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In its fulness, the gospel includes all the doctrines, principles, laws, ordinances, and covenants necessary for us to be exalted in the celestial kingdom. The Savior has promised that if we endure to the end, faithfully living the gospel, He will hold us guiltless before the Father at the Final Judgment (see 3 Nephi 27:16).
The fulness of the gospel has been preached in all ages when God's children have been prepared to receive it. In the latter days, or the dispensation of the fulness of times, the gospel has been restored through the Prophet Joseph Smith."
http://lds.org/study/topics/gospel?lang=eng
Do you believe that they were under the fulness of the gospel from Adam to Moses? What evidence do you have that they were under the fulness of the gospel during this time period?