I guess this proves both OSAS and NOSAS are Biblical if Amill is Biblical, since there are those who are Amill who are in the OSAS camp, and there are those who are Amill who are in the NOSAS camp. As to Premill, there are those who are in the OSAS camp, and there are those who are who are in the NOSAS camp, except neither of these doctrines affect that position whatsoever. Per Premill, one is either already eternally saved or eternally lost before anyone ever takes part in the first resurrection. Which means one's salvation has already been determined before one is bodily resurrected, the first resurrection. Which means no one can have part in the first resurrection unless they remained saved up until the moment they died. Thus, no one has part in the first resurrection until they are bodily raised first.
NOSAS combined with Amill teaches that one can have part in the first resurrection then lose part in the first resurrection before they die. That's not what John in Revelation 20 is saying. Once one has part in the first resurrection one can't then lose part in it. That's what John in Revelation 20 is saying. Therefore, it is impossible that Amill is Biblical if NOSAS is Biblical. While it's not impossible that Premill is Biblical if NOSAS is Biblical. No contradiction whatsoever.
Since I firmly believe the Bible affirms the doctrine of eternal security, I have no doubt that once a person has part in the first resurrection means that person has been born again. And since they have been born again by partaking of the resurrection of Christ, Who is the first resurrection, they have at the moment of new birth entered into the Kingdom of God, having eternal life.
John 3 shows us that to understand (see) or enter the Kingdom of God we MUST be born again. If we've entered the Kingdom of God through re-birth, which is having part in the resurrection of Christ, there is nothing that will take us from His Kingdom. Why? Because we were admitted into His Kingdom through the work of Christ alone. It was by His perfect life, death and first resurrection from the dead that we were welcomed into the Kingdom of God. Our participation in the first resurrection, i.e., being born again through Him is ALL of Christ and for His glory. Just as we had no part in our physical birth, we have no part in our new birth.
However, after the Holy Spirit has come into our hearts, giving us eternal life through Christ our responsibility is to repent, turn to Christ so the life we have through partaking of His resurrection will be made known by our changed lives. When we have partaken of the resurrection life through Christ, we are not the same and our lives will reflect the new person we've become. But the new eternal life we've received is kept by the power of God in us, (1Pe 4-5) and even though we stumble and fall many times after our new birth, we can never be lost again IF we have truly been born again of Christ.
Now we have entered the Kingdom of God through new birth while alive in this world. What happens to us when we die? We enter into the Kingdom of heaven as living (spirit) soul. But it was in life, when we partook of the first resurrection through Christ that we lived and reigned with Christ in time (likened to a thousand years). That's why John says, "they lived and reigned", with Christ a thousand years. That is during this symbolic time likened to a thousand years we had part in the first resurrection, spiritual re-birth. So, in death the symbolic time of a thousand years has not yet ended, but after believers have died we are no longer living and reigning with Christ a thousand years because we have passed from time that exists on the earth into eternity in heaven.
According to John (Rev 20:6) there are still others alive on earth during this time symbolized a thousand years. Some of them will be called blessed and holy by partaking of the first resurrection, by re-birth during this time likened to a thousand years, who will also live and reign with Christ during this time of physical life on earth. Since they have part in the first resurrection the second death has no more power over them. Because when they die, they too will enter into eternity as living (spirit) souls, who have passed from time on earth (a thousand years) to eternity in the Kingdom of heaven.
But as John tells us the rest of the dead, or those who have never and will never partake of the first resurrection (new birth) in time likened a thousand years, will not come alive again until time symbolized a thousand years is finished. They will be called to stand before God at the GWT to give account for their lives on earth according to what is written in books. And since their names will not be found written in the Book of Life, they must face the second death that is the LOF.
There is nothing here that I have not told you before David. I suppose to keep repeating myself may serve a purpose, or at least get you to search the Scriptures to see if these things be true. I don't believe by this point you cannot see the problems with the doctrine of Premill. Nor do I believe by this point that you have refuted the doctrine of Amill, though you continue to fight against it by bringing in new arguments.
I will conclude by saying I agree with your assessment of eternal security and the doctrine of Amill, and Premill for that matter. No matter what eschatological position one holds to if we have partaken of the first resurrection through the resurrection life of Christ or have been born again of the Spirit of God we are eternally secure and can never die! Not my words, but the promise of Christ.