Salvation Through the Ages, Chap. 2, The Age of Innocence
From Creation to the Fall
This age is characterized by the creation of Adam and Eve as innocents. They had not yet disobeyed God and everything God created was "very good". But mankind, a sentient being, had the capacity to either obey God or defy him. Some will say that God put the one restriction against eating of the Tree of the Knowledge of Good and Evil to tempt them, but the scriptures clearly say that God tempts no one. Our potential for sin comes from our sentience, our free will. So in theory Adam and Eve could have sinned by disobeying any of God's commands, which included managing the earth and "multiplying". But they failed to obey God in everything, and at the moment of that first sin innocence was lost. They could no longer enjoy direct communion with God, and physical death would be the fate of the first humans and all their offspring.
So what meaning did salvation have in this age, before sin had entered the world? There was nothing to be saved from, no one needing rescue or redemption; nothing was wrong. So before sin there was no concept of salvation. However, as other scriptures make clear, God had already made a plan to take effect at the end of this age. He confronted the serpent and told of its eventual demise at the hands of "the seed of the woman", the one the serpent had targeted directly with malicious trickery. Yet this was to come only after thousands of years.
Did Adam and Eve go to heaven? We are not told; we can only make arguments from silence. Yet clearly any means of salvation for them could not involve believing specifics about Jesus coming as a sacrificial Lamb, or obeying the yet-unknown laws of Moses. Adam and Eve had one command to obey, were told ahead of time what the penalty was, and were separated from direct communion with God as a result. There was nothing said about how this might be remedied at that time.