For as in Adam all die, so also in Christ all will be made alive. 1 Cor 15:22
Adam was never the full intention of God when He created man. Adam was a beginning, but not an end.
...Adam, who is a type of him (Jesus) who was to come. Rom 5:14
When God created Adam, He was making man in His image - this process would not be complete until all men, who would choose Jesus when their opportunity was provided, were part of the Kingdom of God. The kingdom of this world with it's evil ruler is not what God intended life to be like for eternity.
Jesus is the firstborn of this new Kingdom because he is the first to be raised into spirit life (which he never had before, being put to death in the flesh 1Pet 3:18).
Previously only the Father was immortal 1Tim 6:16, but now Jesus is also - having life as the Father does John 5:26, because God gave it to him at his resurrection (never to die again Rom 6:9).
Making man in God's image would not include a creation of death! But when all are given life as Jesus now has - this is what God intended all along.
because those whom He foreknew, He also predestined to be conformed to the image of His son, for him to be firstborn among many brothers. Rom 8:29
How is Christ "firstborn of all creation" ?
Colossians 1:15 "[Christ] is the image of the invisible God, the firstborn of all creation"
Paul plainly expresses how CHRIST is God's image. We are in God's image IN Christ because only in Jesus is death resolved. Only by grace are we renewed to the status of having Kingdom potential. No man has this potential outside of Jesus.
So yes, Jesus is only the firstborn when he was raised from the dead and 'born' into eternal life with God.
Jesus himself spoke of being 'born from above' John3. This echoes the birth of a person in a physical sense, of the flesh, with the second 'birth' of the spirit. Adam did not have a birth, so being called the firstborn seems rather silly, but he will (probably) be born from above at some time yet future with the 'all who ever lived'/'rest of the dead' Rev 20. ('born again' is not a biblical term and it does seem odd when speaking of Adam who was never born a first time.)
Obviously, others were raised from the dead, but none to spirit life. No man has ascended to heaven except Jesus John 3:13.
Colossians goes on to put his 'firstborn' into very unequivocal context. There is no need to make assumptions here.
15He is the image of the invisible God, the firstborn over all creation, 16because in him were created all things in the heavens and upon the earth, the visible and the invisible, whether thrones or lordships or rulers or authorities; all things have been created through him and unto him. 17And he is before all things, and in him all things hold together. 18And he is the head of the body, the church, who is the beginning, firstborn out from the dead.
As the firstborn of creation, Jesus cannot be the Creator! "Christ is Adam's creator", as one comment purports. This is profoundly unbiblical. Any alleged scriptural support is purely suppositional and requires us to read-in a traditional belief system which no NT author teaches.
Jesus said, '...(I am) a man who has told you the truth - that I heard f r o m God! John 8:40. God is the Creator not Jesus or the Christ, God raised Jesus, not Jesus, God is the only immortal being, Christ died. Jesus is the firstborn of creation - not because he is THE Creator, but because he is the triumph of God over evil, sin and death which allows humanity to have a future past this age - "in Christ all will be made alive".
The relationship between firstborn of creation and of the dead is explained here