Orochimaru's cursed seals, once released, caused their markings to spread across the body's surface. This was the first stage. The more densely the black markings covered the body, the more thoroughly the power of the first-stage cursed seal could be tapped.
When the cursed seal completely covered the body and fully activated the host's flesh, the senjutsu power within it would cause mutation. To adapt to that alien, immense power, both the host's mind and body would grow agitated and run wild. Kimimaro's second stage of the Cursed Seal of Earth even grew a huge Tyrannosaurus-like tail. It was absurd enough.
As for the cursed seal's third stage—Wu Yu guessed that, if it had to be classified as a third stage, it would undoubtedly be "the cursed seal fully activating, allowing Orochimaru to reincarnate through a new vessel at any time."
At the time of Sasuke and Itachi's decisive battle in the original timeline, Orochimaru had taken advantage of Sasuke Uchiha's exhaustion and inability to suppress the cursed seal on his body, directly activating it and returning to the present world as Yamata no Orochi.
Later, during the Fourth Shinobi World War, Sasuke Uchiha used Anko Mitarashi's cursed seal to revive Orochimaru, and even then, he needed to borrow a piece of flesh containing Orochimaru's DNA from Sage Kabuto. But Sasuke himself, during his battle with Itachi, had devoured everything Orochimaru possessed. He naturally carried everything necessary for Orochimaru's resurrection.
With a fully activated cursed seal, taking even a tiny piece of Sasuke Uchiha's flesh was enough to achieve rebirth—
Tsunade's version of the cursed seal was clearly still missing something if it was to produce the same effect.
Although the Chakra of first-rate shinobi could contain their own will, masters such as Minato Namikaze could even use the Chakra