Was Adam to have eternal life if he did not sin? What was his first day, since he was to die in the day he did sin?

Your question reflects an ignorance of Scripture; a theological laziness. Death in this context is spiritual, being removed from the presence of God.

A physical being or an animal is destined to die a physical death, regardless.

Ephesians 2:1  And you hath he quickened, who were dead in trespasses and sins;

Ephesians 2:5  Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;)

Colossians 2:13  And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;

1 Peter 2:24  Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed.

John 11

25 Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live:

26 And whosoever liveth and believeth in me shall never die. Believest thou this?

John 6

66 From that time many of his disciples went back, and walked no more with him.

67 Then said Jesus unto the twelve, Will ye also go away?

68 Then Simon Peter answered him, Lord, to whom shall we go? thou hast the words of eternal life.

69 And we believe and are sure that thou art that Christ, the Son of the living God.

Genesis 3:8 And they heard the voice of the Lord God walking in the garden in the cool of the day: and Adam and his wife hid themselves from the presence of the Lord God amongst the trees of the garden.

John 5

21 For as the Father raiseth up the dead, and quickeneth them; even so the Son quickeneth whom he will.

22 For the Father judgeth no man, but hath committed all judgment unto the Son:

23 That all men should honour the Son, even as they honour the Father. He that honoureth not the Son honoureth not the Father which hath sent him.

24 Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.

25 Verily, verily, I say unto you, The hour is coming, and now is, when the dead shall hear the voice of the Son of God: and they that hear shall live.

26 For as the Father hath life in himself; so hath he given to the Son to have life in himself;

27 And hath given him authority to execute judgment also, because he is the Son of man.

28 Marvel not at this: for the hour is coming, in the which all that are in the graves shall hear his voice,

29 And shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation.

Genesis 3:9 And the Lord God called unto Adam, and said unto him, Where art thou?

Ask yourself, why was there a "tree of life" also in the garden? Presumably, Adam and Eve would have had to have partaken of this tree to have eternal life. However, eternal life in the creation of the demiurge is not life at all.

You may notice that "god" said, "if you partake of the tree of the knowledge of good and evil, you will surely die". whereas the Serpent told them that "god" was lying, and "you will not surely die, but your eyes will be opened". This is exactly what happened! Their eyes were opened, but they did not die. The Serpent told the truth! God lied. Who will you follow? The Abrahamic "god" or the Serpent, Lucifer?

He was created to be eternal in his physical body, yes. But when he sinned, physical death as well as spiritual death entered into the physical universe.

Sorry, but your second "question" does not make sense.

Through him we have obtained access to this grace in which we stand, and we rejoice in our hope of sharing the glory of God. (Romans 5:2)

MARANATHA! Come, Lord Jesus, COME!

Adam has eternal life from faith in Jesus, same as us

Adam did not exist,

yes