“Will my prayer help?”
And about half of Christianity believes that your prayer does help. The Orthodox church teaches that the the soul obviously lives on. The soul still exists, and it can be still be assisted with prayer. Including it’s final state.
I think we all, in our dim humanity, wish Christianity was a democracy, but it is not.
It is a monarchy.
And the Word of the King, in this monarchy, actually IS the King.
So, the Word of God tells us that men are given “once to die and once to judgment” —nixing the idea of reincarnation, but also pointing that the time to be judged for what we do on earth ends when we die.
... and that same living Word also tells us that necromancy or prayers for, or to, the souls of the dead is not tolerated, but a sin.
“Half of Chrisitianity” may believe prayers for the dead would help but they have been out-voted by the King (of Kings)...
God is His living Word who “was God and is God” and also “the Word that was ... made flesh and dwelt among us.”
Meaning (at the very least) that the words of the King cannot be broken by a majority vote of His subjects.
Praying for people after they die, unless you are thanking God for the person whom you love that is now gone, is pretty futile. This is why we are to “preach the word in season and out of season” and cry out for the harvest of souls — now.