While it is very fascinating, I do not believe that, at this point, it would work the same way in humans even if we did capture the reversing process.
Jellyfish are not as complicated, as far as brain function, as humans are. Interestingly enough, though, many have far more chromosomes than do
humans, so technically speaking, they are more genetically complicated than we are.
Anyway, back to my point. A jellyfish can revert to its polyp stage. This is actually the second stage of a jellyfish's life (not including the eggs
stage), and there are two forms after that. Humans stay relatively the same throughout their entire lives. We do not have radically different forms
like jellyfish do. We also are not capable of asexual reproduction, though I know of some people who are so sick of relationships they wish they
could.
Obviously, the closer an organism is to another, the easier it is to do genetic modification. Therefore, I see the use of the jellyfish being more
along the lines of regenerating lost tissue, prolonging QUALITY of life, etc. rather than making us immortal. Besides, do you REALLY want to go
through teething, puberty, and high school more than once.