THE SINNERS ARE CONFINED IN THE TEMPORARY PRISON

The Sinners are Confined in the Temporary Prison

vs.  5-6

"But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection. Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years."

Therefore complete righteousness during the kingdom. This also deals with the problem of moral environment.

"lived not again"  This phrase clearly indicates bodily resurrection after bodily death. The unsaved dead obviously will not live again spiritually, for they are in hades and will ultimately be in the lake of fire. In fact, the term “resurrection” itself occurs over forty times in the New Testament, and always refers to the resurrection of the body.
"finished" Jesus had referred to “the resurrection of life” and “the resurrection of damnation” (John 5:28-29), and so had Daniel (Daniel 12:2) but here it is revealed for the first time that the first resurrection will be completed a thousand years before the second. The word “is” does not appear in the Greek. The sense probably is that this completes the first resurrection (note 1 Corinthians 15:22,23; Matthew 27:52-53; Revelation 11:11).

The Identity of the Sinners are the Rest of the Dead vs. 5

"But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection."

All the wicked of all the ages are herein referred to. All of these are lost.

The Place of These Sinners is the Hades or Sheol

All evil men go to Hades (cf. Luke 16:19-31).

The Length of Confinement is 1000 Years

This is true of those who are living when Christ comes in Revelation glory. Others who die previous to this event will remain in until the resurrection of the wicked at the close of the Millennium.
The problem of physical environment is ignored in this chapter. See Isaiah 65.