If seeking knowledge (knowledge in relation to sin, or between good and evil) was a sin, then why would Jesus say something like "...and the truth shall set you free" (John 8:32)?
You can't have the truth about right and wrong, without knowing the differences between the two.
But if eating the fruit from tree of knowledge of good and evil is a sin, then Genesis 2 & 3 has introduce a paradox to the story.
If eating the fruit is the only MEAN to "know" right and wrong, then they couldn't have known it is a sin to disobey God, or if God and the serpent is telling truth or lie about the Tree of Knowledge...especially if they have no knowledge of right and wrong, good and evil.
Did the serpent lie?
As far I can see by reading Genesis 3... ...NO.
They didn't die that "day".
There is assumption (often made by Christians) that Adam and Eve were immortal, that there were no death before eating the forbidden fruit. That's assumption is false.
This assumption come from God said to Adam:
Genesis 2:16-17 said:
16 And the Lord God commanded the man, “You may freely eat of every tree of the garden; 17 but of the tree of the knowledge of good and evil you shall not eat, for in the day that you eat of it you shall die.”
It doesn't say anything about death don't exist...it only say that he will die on that day. They were never immortal, even before eating the forbidden fruit. They would only live forever, if they had eaten the fruit from the tree of life (Genesis 2:9), but clearly they eat from that tree (Genesis 3:22):
Genesis 3:22 said:
22 Then the Lord God said, “See, the man has become like one of us, knowing good and evil; and now, he might reach out his hand and take also from the tree of life, and eat, and live forever”—
This verse indicate they were always "mortal".
Death or mortality didn't exist because God place a curse on Adam and Eve in verses 3:14-19.; they were already mortal. 3:14-19 is not about they will eventually die.
No, they will not only eventually die, but while they live, they will suffer. Women will suffer pain through childbirths, and man (and woman) will have to work and toil for their food; if they don't toil for food, they will suffer from starvation.
Their punishment (3:14-19) is that both man and woman (and their descendants) is they will know pain and suffering before they die. 3:14-19 is not about introducing death, but pain and suffering.
Let's say, as an example, they didn't disobey God, so they didn't eat the fruit from the tree of knowledge. Let's also say, they didn't eat from the tree of life too. That mean that they are still mortal...the only difference is that there will be no pain and suffering.
Most Christians that I have known, have jumped to the conclusion if Adam and Eve didn't eat the fruit of knowledge, that they will live forever, but that assumption is clearly false, because they have misread Genesis 2 & 3.
Heck, I used to believe in this same faulty assumption when I was younger. This is why I no longer trust church teaching of the OT bible. And it is not the only flawed and faulty Christian interpretations that I had fallen for. I thought that the serpent was Satan, because I followed the church interpretation to Genesis 3.