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Yes, Mangekyo Sharingan can extinguish it.
He trains he sharingan to achieve the Mangekyo.
to see how strong naruto was and if he was stronger 2nd time to get mangekyo sharingan
Sharingan is not a jutsu. It is a kekkai genkkai or blood trait, like the byakugan. It a secret ablity only members of the Uchiha clan(sasuke and itachi's clan) has. The jutsus that can be performed using a sharingan are a kind of 'doujutsu' (eye techniques), along with byakugan and rinnegan techniques.
A Mangekyo Sharingan is an awakened, advanced form of Sharingan. Characters have unlocked it by killing someone close to them.
That would have to be Madara Uchiha. With his Sharingan, Eternal Mangekyo Sharingan that makes him untouchable, and his ability to teleport anywhere, he is definitely the most powerful villain in the Naruto world.
Sasuke's mangekyo sharingan.
If you mean Shisui, he has the sharingan. However, when Itachi kills him, Itachi gains the mangekyo sharingan, and that's what you probably meant.
In the manga, Madara implanted Itachi's Mangekyo Sharingan into Sasuke's almost blind eyes. Therefore, the two Mangekyo Sharingan create Eternal Mangekyo Sharingan, restoring Sasuke's vision and preventing all future damage to his eye by using Eternal Mangekyo Sharingan. His Eternal Mangekyo Sharingan is yet to be seen.
Sasuke already have Mangekyo Sharingan after fighting with Itachi. If you are asking about Eternal Mangekyo Sharingan then on latest chapter of manga he asked Madara for Itachi's eye. If he implants it then he will have Eternal Mangekyo Sharingan. We'll have to wait and see the upcoming chapters.
Yes, Itachi went blind because he used his Mangekyo Sharingan multiple times with the Mangekyo Sharingan's use, it starts to corrode your vision. The only way to restore your vision and not have any side effects of using the Mangekyo Sharingan is to plant another person's Mangekyo Sharingan into yours.
No, just Sharingan and Mangekyo Sharingan.