It is possible to awaken a new Rinnegan by obtaining Hagoromo's chakra, either by combining the chakras of his sons, Indra and Asura, to create his own, or by directly receiving it from Hagoromo himself. Black Zetsu spent centuries attempting to manipulate the reincarnations of Indra and Asura into awakening the...
Indra has three times awakened as one would expect from the eldest son, but Asura only once, causing trouble for Black Zetsu who had planned on using him as a host body. However, Asura's death at Black Zetsu's hands allowed him to revive, this time with the name "Rin" and the appearance of Rinnegan, which he has not yet used even after thousands of years.
Black Zetsu also tried to use Kaguya-hime's chakra as conduit to awaken Rinnegan, but was stopped by her father, Amaterasu. Finally realizing that she will never allow herself to be used as a weapon, he decided to destroy her instead, but was defeated when Amaterasu absorbed all of Black Zetsu's power before killing him.
As for Hagoromo, we know that he survived the battle with Black Zetsu due to being protected by Indra's jutsu, which tells us that he is still alive.
No, not at all. To activate the Rinnegan, both Indra and Asura chakra are necessary. Only a Uchiha who is Indra's reincarnation, and only if he is granted Asura's chakra, may awaken the Rinnegan. Only those like Madara, Sasuke, and other Indra reincarnations have the ability to activate the Rinnegan.
Furthermore, even if they could awaken the Rinnegan, there is no guarantee that they would be able to use them. The reason for this is that, in order to use the Rinnegan, you need to be an Asura. Thus, only someone with Asura chakra can use it. However, since only Indra can grant Asura chakra, only someone like Madara or another Uchiha who is his reincarnation can use the Rinnegan.
In conclusion, only someone who is an Indra reincarnation and who has been given Asura chakra may awaken the Rinnegan. Even then, there is no guarantee that they will be able to use them.
Because he was Indra's transmigrant, Madara was able to awaken the Rinnegan. During his struggle with Ashura's transmigrant, Hashirama Senju, he chewed off a chunk of Hashirama's flesh. This blood contained cells from both humans and animals, which allowed Madara to learn how to wield the Rinnegan.
After this incident, Madara began collecting organs from deceased villagers in order to further his research on immortality. He also started gathering bones from battlefields around his village because he wanted to conduct experiments on them. However, since none of these sources were enough to complete his research, he decided to steal bodies from a nearby graveyard. However, due to Hashirama's guard dog, Gin, being with him in the afterlife, even Madara could not overcome this obstacle. So, he decided to kidnap people instead.
One night, while everyone else was asleep, Madara sneaked into a house and kidnapped a young boy named Tsunayoshi Sawada. He took Tsunayoshi to his laboratory and began experimenting on him. However, during one of these experiments, Tsunayoshi woke up and ran away. When Madara found out that someone had seen him, he went after Tsunayoshi again but this time with his army of sandworms.
Nagato gave Obito the same rinnegan, which he used in the Fourth Ninja War. When Madara awakened the rinnegan by combining the reborn ashura chakra within Hashirama with his own Indra chakra, he awakened the rinnegan, and his eyes were transplanted into Nagato when he died, and then to Obito when he died.
Obito has access to the Six Paths and all the benefits that come with them, such as shared vision, thanks to the Rinnegan. Keeping his Sharingan, on the other hand, grants him access to Kamui and chakra awareness. He can also use his Mangekyou Sharingan to view the truth of things, but this requires a lot of energy and can only be used for a limited time.
In terms of power, the Rinnegan are superior to the Mangekyou Sharingan. This is because they don't require energy to use and can see into the future. The Mangekyou can only be activated for short periods of time due to its immense power requirement. Even so, the Rinnegan are still powerful enough to destroy an entire city.
As for what Obito could do with his Rinnegan, he could read any type of book or document, even those written in kanji. He could also look at paintings and drawings and see their true colors. Finally, he could gaze into people's eyes and see their souls.
When it comes to fighting, the Rinnegan allow Obito to see through attacks and avoid getting hit himself. He can also use his Mangekyou mode to destroy objects and take out large groups of enemies at once.
After obtaining the DNA and Chakra necessary to gain the Rinnegan, you must wait precisely five years IRP to begin seeing the effects. These are your odds of getting a certain stage of the Rinnegan. There is no way to speed up the process.
In order to obtain all four eyes, you will need to wait for five years after gaining each one separately. As soon as you gain one eye, new tissues grow in its place, making it difficult to tell where one tissue ends and another begins. This means that you could have already obtained a second or third eye even though you don't know it yet!
It is important to note that while you are waiting for these eyes to develop, there is nothing stopping you from using themies.
If you go more than five years without viewing an image in a mirror, you will eventually lose track of what you look like and become disoriented when trying to find your way out of a room. If this happens to you, take out your smartphone and scan something. You will then be able to see in your reflection again.
However, if you leave the world of the living for too long of a period of time, you will die. So be sure to keep yourself occupied by playing games, reading books, etc. during your wait.