There are numerous places in Scripture that discuss the dead having the chance to choose salvation. I'll get to the specifics in a minute. You cannot overlook Church Tradition, which to Catholics is just as important as Scripture.
As far as Tradition goes, you must explain to me the concept of praying for the dead. If, when you die, you go to heaven or hell praying for the dead is a waste of effort. If the dead do not go to heaven or hell then where do they go? Catholics invented purgatory. We could have called it something else, but we called it purgatory. If you expect me to believe the stuff about indulgences, and saying so many prayers means you don't have to spend 300 years in purgatory you have a real tall task to accomplish. I do believe in Purgatory, I believe it is a third place souls can go after death. What happens there is vague. Certainly there is the purification of your soul but no real mention is made on how that is done, or how long it takes. In all fairness, I don't think the Church fully embraces Scripture in this area.The Church seized this area to made a bunch of money in the past but I think it has gotten away from that now.
Read 1 Peter 4. I guess this is controversial. I've read all of 1 Peter and, in my opinion, Peter is not referring to death as death in the spirit. Peter is referring to death as being dead and buried. So then you must explain away the passage, "But they will have to give account to him who is ready to judge the living and the dead." and "For this is the reason the gospel was preached even to those who are now dead, so that they might be judged according to human standards in regard to the body, but live according to God in regard to the spirit." This passage, while confusing, and evidentially not just to me, does do a good job of making you think. Assuming Peter was not on crack, what is he talking about?
Then there is the overall view of God and man. We know God loves us, that He is a just God, and that He has gone to great lengths to help us. He sent Jesus to purchase our salvation. That shows me how much God loves us. When you read the Bible I think it is fair to have the predisposition toward the forgiveness and love of God. The idea that Jesus will judge the living and the dead supports the concept that judgement will come at a unique date. That people will just be dead until that date and there will be some people alive on that date. If you believe that, then Peter seems to say that the Gospel will be preached to the people that are dead, prior to judgement. That makes sense. I'll grant you that most of Scripture indicates we are to be judged on what we do before we die, but I do wonder about this.
To the best of my knowledge, Jesus has no restrictions on His judgement. He can allow Judas or Hitler or me into heaven, or send Peter, or Mother Theresa or me to hell. About all we can do is realize that God has done a great deal of work to get us into heaven; He must want us there. Since we actually know very little about what our state of being is after death, the idea that we will hear the gospel during the time we are dead is comforting. I couldn't find the passage I really wanted to find, but this one is interesting. Why preach the Gospel to those that will be condemned to Hell?
Honestly, I don't have it all figured out.
Read the Catechism and the notes in your bible on Peter I Chap 4. Several interpretations are given and neither one of them excludes the others. On the one hand he may be referring to the righteous who died before the coming of Christ and were held, according to the old Testament, in the bosom of Abraham where they waited for salvation to be effected. The Gospel was preached to them before entering heaven so they would know the fullness of their salvation. It may also refer tho those who have and have not heard the Gospel. Those who have heard the Gospel and accept are the living, those who have not yet heard the Gospel are the dead. Both hear the same Gospel preached to them.
Those who reject God in this life condemn themselves to hell where they will go when they die. At death, the choice a person makes in this life becomes irrevocable. That is what the Church teaches.
We judge ourselves by the way we live. In both the particular and the final judgement God is confirming your choice.
Indulgences have nothing to do with the number of days or years you spend in purgatory. That was a mistaken understanding most Catholics including religious and Priests when indulgences were specified in number of days or years earned by saying an indulgenced prayer or performing an indulgenced action. Those awards, rather, specified that you earned the same merit as if you you had performed a penance of so many days or years. Exactly what that means for your"time" in purgatory is wholly dependent on the degree of saintliness (your disposition) at the time you said or did the indulgenced prayer or action.
Plenary indulgence, assuming you met the requirements and had the proper "dispostion" does do away with all temporal punishment due to your sin. That is one of the reasons that indulgences are no longer specified in terms or days or years; i.e. to remove the confusion.
The unique date that judgement comes is two fold. Judgement is rendered at the moment of your death a time and place unique to you. At some point in the future, the end of the world comes and that date is also unique. At the final judgement not only do you and God know how you lived but so will everyone else. And at that final judgement all will be judged, both those who have died in all of history prior to the end of the world but also those still alive at that time. Hence, both the living and the dead will be judged.
Since we do not know with certainty anyone's status when they die, it is good and wholesome to pray for the dead. A declared sait we know, infalibly, are in heaven. That does not necessarily mean they went to heaven immediately when they died. But when canonized, we know they are in heaven at that point.
Everyone else to us is a question mark. That is why the Church says absolutely nothing about who is in hell except for the fallen angels, Satan and his minions. We can make educated guesses based on their lives such as Hitler or Stalin, even Judas, but we have no certainty until the final judgement.
The Church's teaching on all this is clear and unambiguous. Start with what the Church teaches and understand the whys and wherefore for its stated teachings.
My personal judgement or yours are immaterial.