How do you imagine the world millions of years from now?

[AFTT47]

In that amount of time we will either be extinct or god-like. I have no idea what form we would take if the latter but I doubt it would be anything we would now even recognize as life.

It is theoretically possible to revive every human being who has ever lived because information is not lost. Whether or not there is a practical way to do it or not, I wouldn't hazard a guess. At some point though, advanced beings should reach the point where the only thing limiting them is the laws of physics.

Once a person dies, how is that "information" not lost? How do we even tell what is going on a live person's head, most of the time? How can that be recovered?

The only thing limiting us now are the laws of physics, and that's not going to change anytime soon, let alone in a million years.

The universe itself doesn't lose information.

We are currently limited by far more than the laws of physics. For starters, our knowledge of it is incomplete. Secondly, there are things we could do in theory but we simply lack the resources to actually do them.