Fair Questions: Did the Righteous Dead reside in Heaven or Hell?

I was asked a follow-up question related to my previous statement on the question of whether or not Hebrews 9 refutes the Real Presence and the Holy Sacrifice of the Mass.  I wanted to provide a fuller answer to this question than the format of Reddit comments really allows.

If it exists in the fullness of time, does that mean it exists in the past as well? That is to say, even if a person died before He lived, His sacrifice exists for them as well? Obviously nobody could have achieved salvation through the Church prior to the establishment of the Church, but since God was always present would it have been possible to achieve something like the baptism of desire prior to Christ's arrival? I guess that's what's meant by Christ's "descent into hell/anastasis", but did the souls of those who would be freed by his death actually experience the underworld, or were they in heaven all along from their own perspectives because Christ's sacrifice already existed? Does this explain why Lazarus can be in heaven with Abraham in the parable of the rich man and Lazarus?

It's true that Christ's freeing of the righteous dead from Hades is how those who lived before Christ were saved.

That said, it's important to keep in mind that what the Jews understood as the destination of the dead was Sheol. Both the righteous and the unrighteous dead went to Sheol (rendered as Hades in Greek and Hell in English). Sheol was the resting place of all the dead, whether righteous or unrighteous. From a Jewish perspective, they experienced the underworld, but it wasn't the underworld as Dante Alighieri would present it in the Divine Comedy.

The parable Jesus told about Lazarus and the rich man who neglected him depicts an understanding of eschatology that was given to us when Christ entered the world, not the traditional Jewish eschatology that Christ liberated us from by His descent into Hades and liberation of the righteous dead from the underworld and bringing them to Heaven and the Beatific Vision, establishing a way for us to reach eternal life with God the Father.

If the Kingdom of Heaven and Christ's sacrifice exist outside of time, would any of the righteous dead have actually recognized any time in Sheol? Or when they died were they greeted by Christ because the covenant has been fulfilled in the fullness of time? I'm trying to apply a human understanding of time and causality here, and I know that's meaningless when we're talking about things like this, but I'm curious.

We're getting rather far outside of divine revelation with this question, but I can appreciate curiosity because I have a fair amount of it myself, and I think these kinds of questions are at least worth considering even when there is no firm answer to be had,

It's very true that trying to understand this in terms of the typical worldly experience of time and causality is meaningless here. That said, let's consider some speculative metaphysics for a moment. There are multiple ways it could work, and we can think through the implications of each.

1. One possibility is that Sheol, as a sort of eternal waiting room for all the dead, doesn't have things like aging, entropy, seasons, genetic mutations, or technological progress to mark the passage of time as we generally experience it. If that's the case, then the righteous dead (and the wicked dead) would probably have no real sense of the passage of time regardless of how long they were in Sheol. So when Christ came, it may have seemed very immediate because they had no temporal frame of reference.
2. Another possibility is that the dead did experience the passage of time in some undefined way. In that case, Christ's coming to liberate the righteous dead might seem awfully immediate for some people and awfully late for others. Though I imagine it wouldn't really matter much to them when they were born up into Heaven.
3. Another possibility is that the wicked dead were allowed to experience the passage of time as a sort of punishment, and the righteous dead were not allowed to experience the passage of time because they did not merit that punishment.
4. 
   

I have no idea which of these possibilities might be correct, and though it is fun to think about, it doesn't really matter to me.  In the end, what's important is the resurrection of Love Himself.

Note:  The above is an icon I purchased from orthodoxmonasteryicons.com and gave to some Franciscan friars.  I depicts the Harrowing of Hell, or Anastasis in Greek.