Praying for the dead suggests that once they pass this life that we, or they, can alter their just reward. That then suggests that salvation, and Christ’s work on the cross, was unnecessary because once we die if enough people pray passionately for them then their outcome can change. I do not hold this to be the case.
>>Praying for the dead suggests that once they pass this life that we, or they, can alter their just reward<<
God has no time. You put the limitation of the Earth going around the Sun on God. God is outside of time and your prayers for a living soul has nothing to do with his/her earthly body.
Everlasting life is a promise from God. Not everlasting but asleep or everlasting in suspended animation, it’s everlasting. Period.
False analogy -- those dead are judged and going to heaven or hell. you cannot alter their just reward. Purgatory/final sanctification is the final stage in the sanctification process for those going to heaven.
The salvation, i.e the sanctification process is done by the grace of God, by the blood of the Lamb, but Christ's one-time sacrifice on the cross
as we all die sanctified to a large extent by this grace,and since heaven has no sin, we who are heading to heaven receive this final sanctification/purgatory "before" going to heaven (note this is not a period of time or a place)