I feel like Oda is trying to throw us off here, Imu being 800 years old and him undergoing the eternal youth surgery is a red herring from Oda.
Knowing him, he wouldn’t give us something like this blatantly, I think Iva and Sabo speculating that the Imu he saw is the same person from 800 years ago is Oda trying to throw us off.
I believe that this Imu is a descendant of the original Imu from the Nerona family but is his own person, I also think that he became Imu through awakening a devil fruit that the original Imu had similar to how Luffy became Joy Boy through awakening the Nika fruit in Wano
Also it’ll be revealed to us that he has his own name St. Nerona …… but Imu is his other name through inherited will
Knowing him, he wouldn’t give us something like this blatantly, I think Iva and Sabo speculating that the Imu he saw is the same person from 800 years ago is Oda trying to throw us off.
I believe that this Imu is a descendant of the original Imu from the Nerona family but is his own person, I also think that he became Imu through awakening a devil fruit that the original Imu had similar to how Luffy became Joy Boy through awakening the Nika fruit in Wano
Also it’ll be revealed to us that he has his own name St. Nerona …… but Imu is his other name through inherited will