Not necessarily.
https://strangenotions.com/monogenism-or-polygenism-the-question-of-human-origins/
And Original Sin is a result of our Freedom. In order to choose goodness (God) we must also have the contrasting option of Evil (absence of God). As long as we have the possibility to choose to love God or not, evil will also exist.

The fact that Adam and Eve were only given plants as food, and not animals, is consistent with a perfect original creation in which death was not a part.
"Wherefore as by one man sin entered into this world, and by sin death; and so death passed upon all men, in whom all have sinned." Romans 5:12.

"Because God did not make death,
and he does not delight in the death of the living." Wisdom 1:13

"For God created man incorruptible, and to the image of his own likeness he made him. "But by the envy of the devil, death came into the world" Wisdom 2:23,34
(See also Romans 5:13-21; 6:23; 8:19-25; 1 Cor 15:21-22)
Mankind and even animals were not given flesh to eat, but only plants:
"God said, ‘See, I have given you every plant yielding seed that is upon the face of all the earth, and every tree with seed in its fruit; you shall have them for food. And to every beast of the earth, and to every bird of the air, and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food.’ And it was so. God saw everything that he had made, and indeed, it was very good. And there was evening and there was morning, the sixth day." Gen 1:29-31.

Mankind was not given permission to eat flesh until after the flood:
"The fear and dread of you shall rest on every animal of the earth, and on every bird of the air, on everything that creeps on the ground, and on all the fish of the sea; into your hand they are delivered. Every moving thing that lives shall be food for you; and just as I gave you the green plants, I give you everything. Only, you shall not eat flesh with its life, that is, its blood." Gen 9:2-4

When the redemption of the whole world occurs at Christ's return, animals will again not eat one another:
See Isaiah 11:6-9 and 65:25

Without death before the fall of man, evolution, as it is touted, is impossible. All theistic evolutionists insist on death before the fall of man, yet this is incompatible with Holy Scripture. Thus, to be a theistic evolutionist is to disregard the Scriptures and to cling to man-contrived theories that attempt to explain by natural means what was obviously a supernatural creation.

The vegans of the world either know that they must take Vitamin B12 supplements (as pills or in "fortified" food), or they find out when they begin to suffer the rather ghastly symptoms of hypocobalaminemia (B12 deficiency). Since there were no B12 pills or B12 supplemented foods prior to the 20th century, anyone who ate an all-plant diet would have suffered (and probably died) from a vitamin deficiency.

Supposing for the sake of argument that there was a Garden of Eden and two people living in it named Adam and Eve. Who in the world can tell from Genesis what they ate? Cite some verses. Even if they didn't kill animals, they could have eaten eggs and milk. Why is Adam and Eve's diet the least bit important to Christianity?

Tell that to the millions of vegans in the world.

The following article deals with the question of why Adam didn't die immediately:
https://www.apologeticspress.org/apcontent.aspx?category=13&article=797

Must say, I hadn't heard of Adapa before. Very interesting. The following article contrasts him with Adam and suggests the two are the same person. This would make sense, that there would be corrupted legends floating around that still hold a kernel of truth in them:

http://www.genesisproclaimed.org/Content/Detail/9#.WCOMEC0rLIU

I am familiar with the epic of Gilgamesh. Regarding the idea that Sumerian/Mesopotamian legends are the source of the text in Genesis:
https://answersingenesis.org/creationism/creation-myths/is-genesis-111-a-derivation-from-ancient-myths/
Deals with the flood specifically:
https://apologeticspress.org/APContent.aspx?category=13&article=5194&topic=100

The book (that I own), "The Authenticiity of Genesis" by Bill Cooper deals with this type of thing and also presents a lot of archaeological and textual evidence overlooked by those critical of Genesis:
https://www.amazon.com/Authenticity-Book-Genesis-Study-Three/dp/0950209082

Friend, Christianity is not merely a collection of arguments or a philosophy - it is the Holy Spirit dwelling within you, allowing you to participate with the risen Christ in the mission of His kingdom. What type of Church did you grow up in? Did you never get to intimately know the living Christ? Did you not witness or experience anything miraculous? Did you never experience an answer to prayer? I suppose if I thought that Christianity was a mere philosophy that had no real spiritual empowerment, I might be tempted to think the same as you, what with the hypocrisy of some Christians.

"This know also, that in the last days perilous times shall come. For men shall be lovers of their own selves, covetous, boasters, proud, blasphemers, disobedient to parents, unthankful, unholy, Without natural affection, trucebreakers, false accusers, incontinent, fierce, despisers of those that are good, Traitors, heady, highminded, lovers of pleasures more than lovers of God; Having a form of godliness, but denying the power thereof: from such turn away." 1 Tim 3:1-5

Will, from my personal experience with Jesus as the Lord of my life, I have been blessed with a peace that surpasses all understanding. Walking with Him as my guide has opened all sorts of opportunities to love others and to be blessed by Him. Life is an adventure where He is continually answering prayers and showing himself as I try to submit to Him in all things. To me, life without Him would be empty and meaningless; totally devoid of purpose. I don't know what kind of examples you were given, but true Christianity can only be compared to a resurrection from the dead; one's life goes from dead to alive; You participate with Christ as he breaks the hold of the sin and vices in your life that currently hold you hostage, and leads you on to righteousness; it is true freedom that results from submission to him, when adopts you as a son. You arguing that it is not possible to really know God, or that the Christian God is false, is like arguing that it is not possible to know my wife or children, or that they do not exist, when I'm telling you, I do, and they do.
Friend, I do not believe that you can be truly joyful without him; you need him as much as I do. He can do for you what he has done for me. While I was raised protestant, like you, the Lord has led me to the Catholic Church, which can be described as the fullness of the faith. If I could give you one suggestion: Start looking up miracles of Saints throughout the ages. Also, Eucharistic miracles. While of course nothing prevents a skeptic from dismissing all miracles as impossible, miracles in the lives of the saints is exactly what we would expect since Christianity is true. While this does not take the place of miraculous experiences in your own life, it is a starting point.

Regarding your previous comment about Genesis; it is clear that men and women were only given plants to eat.

Human beings cannot survive on a purely plant-based diet.

Depends on your definition of "generation". Christ also said (in John chapter 2), “Destroy this temple, and in three days I will raise it up.” The Jews then said, “It has taken forty-six years to build this temple, and will you raise it up in three days?” But he spoke of the temple of his body. When therefore he was raised from the dead, his disciples remembered that he had said this; and they believed the scripture and the word which Jesus had spoken.
Jesus gave prophecies which were not always clear to the recipients until their fulfillment was happening. It is evident that he intended it this way. Since Christ sometimes spoke with this type of mystical language, it is not sensible in such a prophecy to expect to be able to sense its meaning upon a cursory, literal reading. This is common in the Holy Scriptures; In Joel 2:31 and Acts 2:20 where it says, "...the moon will be turned to blood." Does anyone actually believe the moon will literally turn into blood? Thus it is completely reasonable to conclude that Christ didn't intend the word he used, "generation" to mean it in the sense of "lifespan". Alternatively, I already suggested that some commentators interpreted this prophecy as referring to the destruction of Jerusalem in 70 AD which was an apocalyptic event for the Jews there.

Of course the disciples were expecting the imminent return of Christ; all Christians do. Christ explicitly confirmed that the details of precisely when he will come are not known by man: "But about that day or hour no one knows, not even the angels in heaven, nor the Son, but only the Father."

If I say: "I'll be there next month, but I don't know exactly what day", it doesn't invalidate the fact I gave a time frame. Jesus says clearly that some of the disciples will not taste death, and that "this generation will not pass". Not knowing the exact time does not change the fact that a specific time frame was given.

Regarding your previous comment about Genesis; it is clear that men and women were only given plants to eat. (Gen 1:29). This changed after the flood (Gen 9:3). In addition, I know of no one who does not see the tree of life as representing a means of eternal life (the opposite of death) and the expulsion from Eden as representing the curse of separation from the paradise God intended for the pinnacles of his creations.

Regarding Pharaoh, the following is an informative article helping to explain your objection:
https://www.apologeticspress.org/apcontent.aspx?category=11&article=1205

There is no shortage of liberal scholars who are eager to apply higher criticism to texts they dismiss as the ramblings of religious zealots of antiquity. Yet an analysis of Church history affirms solid evidence for the authenticity of all of the canonical books, including 2 Peter:
http://www.newadvent.org/cathen/11752a.htm

Of course the disciples were expecting the imminent return of Christ; all Christians do. Christ explicitly confirmed that the details of precisely when he will come are not known by man: "But about that day or hour no one knows, not even the angels in heaven, nor the Son, but only the Father."

Matt 24:36
"Therefore keep watch, because you do not know the day or the hour." Matt 25:13
But whether you die or Christ returns; the result is the same - salvation or damnation.
Friend, you seem to like arguing... I suspect you could argue in circles for the rest of your life, convincing yourself of your own theories as you go. It is strange to have your own made-up religion, which is based solely on your own whims, but I suppose some like to be their own gods... you could call it the Church of Will. I prefer the Church whose history stretches back to Christ through the apostles.

“We do not really want a religion that is right where we are right. What we want is a religion that is right where we are wrong.” -Chesterton, The Catholic Church and Conversion

“The Christian ideal has not been tried and found wanting; it has been found difficult and left untried.” – Chesterton, Chapter 5, What’s Wrong With The World, 1910