the cells have now differentiated into other organs and locked into that process biologically
well in a sense loosely locked.
But locked none the less.
You have already grown from that state that differentiated into a human.
The same way we cannot drop a cell on the ground like a seed and expect a new human to grow from it.
But it can be possible to clone perhaps?
If you remember the cloned sheep Dolly,
The major problem was the telomere lengths of the clone.
Biologically it seemed to carry from the point of the living sheep to the clone
Which died.
In a sense the clone (if I remember correctly) was born with pre aged cells.