2 part 1: The Plan Revealed
This part has the technical details that go over how their plan will work. The whole episode all together is a bit hard to follow for some, as it deals with some pretty complex technical processes. The actual science involved is a bit more complex that we as a society are capable of, so this is as good of an explanation as I can get. If you can get through the three part episode, you should have a really good start at understanding the context behind the other episodes.
2 part 2: The Genome Changes
Genetics in extreme long life pose very different challenges than in a normal lifespan. The fictional doctor Strano-Amore goes over the details of what helps them be successful in their “leap”
2 part 3: Multiverse Theory 101
One of the most odd things for me to understand was Multiverse theory. Since in real life it works nothing like what is available in any science book or article available now, getting even this very rough outline of how it works took a while. Granted, this is somewhat like the equivalent of kindergarten version of nuclear physics, but it is as accurate as possible without a large foundation of knowledge that our science just has not discovered yet. Either way, it is essential to understand the concept, as it is central to the history of their society, and how everyday life their works. I did write an article or post about this available on this site, if you need further reading.