It's difficult to say whether or not Adam knew what death was. The Society says, he knew because no doubt animals died and he witnessed it. But the scriptures don't say. Not that I believe animals were made to live forever, then again. Adam and Eve were vegetarians before the fall. In the animal kingdom when animals are dying, they crawl off somewhere to die, so you won't see their carcass. We see them today, because they get hit by cars and are killed by people for sport or cruelty.
That said, I don't think Adam thought it through. Yeah, he was perfect, but he was only a few years old at most, a child in a man's body, still learning, questioning. He's alone, God decides to give him a companion, "it's not good for man to be alone" he says, which is silly, because God knew exactly what He was doing. He was teaching Adam about companionship, loneliness and love. After-all, how else was the earth to be filled?
So Adam has a companion, a wife, a helpmate. She's deceived. Adam remembers what Jehovah told him, "in the day that you eat of it you shall surely die." Now he reasons, "I'll be alone again." He didn't reason, "God will give me another companion", or maybe he did and decided he didn't want another one, he wanted Eve. "If she dies, I'll die with her" and partakes of the fruit. Suicide.
Now based on my study of the scriptures, I don't believe Adam suffered eternal death. Based on my studies on the meaning and philosophy of the word RANSOM, I believe Jesus died for Adam, a life for a life and in redeeming Adam, he redeemed ALL those who came from Adam's loins, the world of mankind. In that way, Jesus, as the scriptures tell us, died "a ransom for all" to be testified in due time.
During the millennial kingdom, everyone who ever died will be resurrected and taught of Jehovah. Free from the wiles and influences of the adversary. They will learn what God did for humanity through the person of Jesus Christ. And during that period, they will grow in grace and knowledge and in due time human perfection. In the end, during the "little season" when Satan is let loose, humanity will be tested as Adam was.