The thing to do now is to look at the passage verse by verse:
20:4 And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of
them that were beheaded for the witness of Jesus, and for the word (o. logos) of God, and which had not
worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their
hands; and they lived and reigned with Christ a thousand years.
20:5 But the rest of the dead lived not again UNTIL the thousand years were finished. This is the first resurrection.
20:6 Blessed and holy is he that has part in the first resurrection: on such the second death has no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.
This first resurrection is of these souls who were physically killed in the tribulation, yet now live again, as priests and kings. It excludes "the rest of the dead". So what happens to them?
20:7 And when the thousand years are expired, Satan shall be loosed out of his prison,
20:8 And shall go out to deceive the nations which are in the four quarters of the earth, Gog, and Magog, to
gather them together to battle: the number of whom is as the sand of the sea.
20:9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the
beloved city: and fire came down from God out of heaven, and devoured them.
20:10 And the devil that deceived them was cast into the lake of fire and brimstone, where the beast and the
false prophet are, and shall be tormented day and night for ever and ever.
20:11 And I saw a great white throne, and him that sat on it, from whose face the earth and the heaven fled
away; and there was found no place for them.
20:12 And I saw the dead, small and great, stand before God; and the books were opened: and another book
was opened, which is the book of life: and the dead were judged out of those things which were written in
the books, according to their works.
20:13 And the sea gave up the dead which were in it; and death and hell delivered up the dead which were in
them: and they were judged every man according to their works.
20:14 And death and hell were cast into the lake of fire. This is the second death.
20:15 And whosoever was not found written in the book of life was cast into the lake of fire.
So here is another group, also pictured as being delivered out of a state of physical death, after the thousand years separating it from the first resurrection.
There are no saints who were spiritually dead (yet still saints) just now gaining spiritual life, and no spiritual life ever given to those who physically died spiritually dead. All we see here is physical death followed by renewing of physical life of two separate groups.