I am trying to make the point that this was the time the Lamb arrived in heaven. I have used the fact that he was slain, the songs in heaven, and the fact that there is only one time in history that Jesus would not have had the scroll was the time he spent as a man. The time that Jesus emptied himself of his glory ends right here.
Jesus is the only way to heaven for mankind. This was God's plan before creation is what is meant by "the Lamb slain from the foundation of the world." Those who died before this scene, those who believed in the God of creation, were saved on credit; but were not able to enter heaven until after this scene.
But it didn't happen until the time of this scene. This is the time heaven was prepared.
The 24 elders are created beings that have been in heaven. The 24 who served in the tabernacle on earth followed the pattern of what existed in heaven. Everything on earth in the tabernacle was does exactly as it was in heaven.
I agree that John saw the whole thing, but the starting point of the visions was at Jesus' ascension into heaven.
The Lord said unto my Lord, sit at my right hand until I make your enemies your footstool.
Jesus wasn't yet seated in Rev 5. How could everyone else beat him there?
The Lamb was always in heaven. Jesus is the alpha and omega, the beginning and the end. The Lamb never arrived, because the Lamb always was.
Can you look at is this way:
The Lamb was not the baby in the womb of Mary. The Lamb was not the toddler under foot of Joseph the carpenter. The Lamb was not an adolescent. The Lamb was not an adult. The Lamb was not even the baptized Jesus with His disciples. The Lamb was slain from the foundation of the world. Jesus from the very beginning, the Word, speaking everything into existence, was the post resurrection Jesus. Throughout the OT Jesus was referred to as the Word. The Post resurrection Jesus appeared to Abraham and ate in Abraham's tent. So the Lamb arriving just like the whole symbolism, cannot be expressed in earthly time. The Lamb as symbolic was always slain.
John was in our present time in heaven, and was seeing all the events surrounding the Second Coming. Not even John arrived in heaven in the first century. John arrived very close to the time of the Second Coming to earth. John saw that no one was worthy to open the Lamb's book of life except the Lamb slain from the foundation of the world.
Of course Jesus was seated. Do you think Jesus has been standing since Stephen was stoned to death?
"But he, being full of the Holy Ghost, looked up stedfastly into heaven, and saw the glory of God, and Jesus standing on the right hand of God, And said, Behold, I see the heavens opened, and the Son of man standing on the right hand of God."
"And I beheld, and, lo, in the midst of the throne stood a Lamb as it had been slain, And he came and took the book out of the right hand of him that sat upon the throne."
How does one stand in the midst of a throne?
Jesus stood up and took the book out of God's hand. Jesus did not just arrive, but was always there. Jesus did receive the book soon prior to the Second Coming. The opening of the 6th Seal is the Second Coming. The 5th Seal is the entire church body in the air glorified in the sight of the entire earth. Then they were told to wait a little while until Jesus was finished with the final harvest on the earth. The Trumpets and Thunders are the final harvest.
The church has been gathering in Paradise since the thief on the Cross entered that day. They have physical bodies, and have been serving God day and night in the heavenly temple and there is a literal alter. The scene in the last half of Revelation 7 is the entire church from Abel to the last person raptured in the 5th Seal. But the entire OT congregation has been there since Jesus ascended Sunday morning, and presented the firstfruits to the one sitting on the throne.
The starting point of John writing down his prophecy was on the Lord's Day, the last Millennium of this current creation. John saw the events leading to the Day of the Lord, starting with the first Seal opened. The 6th Seal is Peter's baptism of fire in 2 Peter 3. The Day of the Lord comes as a thief in the night. That is from our perspective. In heaven they watched the Seals being opened.
If WW3 breaks out and 2 billion people die, we may know that the Second Coming is about to happen. If the Second Coming is part of that 2 billion, then perhaps half of that amount will be raptured out of death, as Jesus is preventing more people from destroying themselves via war. We have Zechariah 14 to set the stage of the symbolic war in Revelation 6, led by death, sheol, famine, plague, and even the animals turning on humanity.
But the 144k are still on the earth after Jesus and the angels arrive. They are the firstfruits of the Millennial Kingdom. They are part of those who are removed from Adam's dead corruptible flesh, like the rest of the souls still waiting in Paradise. In fact those in Paradise wait until the NHNE, and come to earth as the New Jerusalem.
The final harvest is who waits on the sea of glass, and return on white horses in Revelation 19. They all are the first generation of the Millennial Kingdom on the earth. These are post Second Coming redeemed. That is why their song is new.
There are no unredeemed in the Day of the Lord. The first generation is entirely redeemed humanity living without sin, sin natures, nor is there death and dying from natural causes. The first act of disobedience results in permanent death and removel from society. Unlike Adam and Eve who lived in a state of death, those who disobey are considered accursed, and they wait in Death to stand as dead at the GWT. Or they are tossed immediately into the LOF. We are not told where they go. But they certainly are no longer alive on the earth. Sin is not allowed to enter.