While in school together, Sirius once tricked Snape into almost entering the Shrieking Shack while Lupin was there, transformed into a werewolf. James realised the danger and stopped Snape, saving his life; this is the incident Dumbledore referred to at the end of the first book.
According to the Harry Potter series by J.K. Rowling (Harry Potter and the Prisoner of Azkaban ), Sirius Black played a prank on Severus Snape by telling him how to get past the Whomping Willow so he could see what Remus Lupin and the rest of the Marauders were up to.
The answer is that Sirius wanted to deflect attention from the real Secret-Keeper. He probably hoped Voldemort would go after him so he could steer attention away from Pettigrew.
Snape hated Sirius mainly for bullying him.
Snape hated Sirius before Lily was ever in any sort of danger from the Dark Lord, and continued to hate him after the Order learned that Pettigrew, not Sirius, was the one who betrayed the Potters.
In GoF, Sirius doesn't believe that Snape was a death eater. He says that he couldn't see Dumbledore allowing him to work at Hogwarts if he'd ever worked for Voldemort. But after Voldemort's resurrection, most people seem to know of Snape's status as a spy.
Harry Potter: Stag
Harry's patronus is undoubtedly the most recognizable. The stag is first seen in Harry Potter and the Prisoner of Azkaban when it saves Harry and Sirius Black (Gary Oldman) from the dementors at the lake.
Snape dies at the hands of Lord Voldemort in the seventh book, at which time his back story is revealed. Despite his attraction to the Dark Arts and Voldemort's ideology of wizard supremacy, Snape's love for Muggle-born Lily Evans, Harry's mother, eventually compelled him to defect from the Death Eaters.
He doesn't trust Snape as Dumbledore does, but he believes that he can detect any disloyalty. Moreover, Voldemort regards Snape as highly intelligent and therefore ' as a true Slytherin ' a person whose top priority is to take care of himself. To his twisted mind, selfless equals stupid.
To keep his cover pretty much. Bellatrix never trusted him and this was her way of trying to prove she was right. There is also the deal with Dumbledore that he must be the one to kill him, so It was pretty much already in action to happen anyway.
Dumbledore seemed to have very little personal affection for Sirius and although he showed some grief after his death, it was mostly because he felt guilty and sympathy for Harry.
Bellatrix Lestrange Killed her own cousin, Sirius Black: She killed Sirius (who was her cousin) during the battle at the Department of Mysteries. She was remorseless and was cackling in glee after she had murdered Sirius.
Harry inherits all of Sirius's possessions, including the house at Grimmauld Place, the house-elf Kreacher, and Buckbeak the Hippogriff.
Amelia Black, the daughter of alleged mass murderer Sirius Black and Sierra Snape, Severus Snape's sister, struggles most of her life to get her father's attention.
The Death Eaters were divided into cells, so each only knew the identities of a few of the others - and it's pretty clear JK Rowling wrote them that way *in order* to explain why Snape didn't know either that Peter was a Death Eater or that Sirius wasn't, as this detail doesn't seem to serve any other plot purpose.
The short and simple answer to your question is “no”. Dumbledore - like the rest of the wizarding world - did not know that Peter Pettigrew set up Sirius to take the fall for his crimes.
We're told in the Karkaroff's trial scene that Voldemort kept the Death Eaters apart so that that none of them knew who all the others were. If you consider authorial intent, the purpose of that scene seems to be to establish why Snape didn't know Sirius was innocent.
He would always resent Harry for being James' son instead of his. Snape even said that he didn't want anyone to find out that he was protecting Lily's child, “especially Potter's son” (pg. 679 of Harry Potter and the Deathly Hallows) because of his hatred for James.
In the final book, “Harry Potter and the Deathly Hallows,” Rowling reveals that Snape was acting on Dumbledore's orders and had protected Harry at school out of love for Harry's mother, Lily. “Snape died for Harry out of love for Lily,” Rowling said.
He was more jealous of Harry than he let on
Specifically, Draco was jealous of Harry. It was easy to miss because Draco didn't often show his emotions, modelling himself on his cold, confident, calculating father, but J.K. Rowling has confirmed that a lot of his enmity towards Harry stemmed from envy.
In this story, Rowling introduces him as the Dark Lord who tried to kill Harry Potter because the boy was prophesied to destroy him.
Harry became so enamoured with the spell that he eventually used it to finish off Lord Voldemort. Here's how Harry's relationship with Expelliarmus became his signature – and why that's a good and bad thing.
Voldemort told Snape he had been a faithful servant, but that he had to regrettably kill him, as he mistakenly believed he was the master of the Elder Wand, as Snape had killed Albus Dumbledore, its former owner the year prior, during the Battle of the Astronomy Tower.
But, despite his maltreatment of Harry and the complicated killing of headmaster Dumbledore (who knew he was a double agent?), Snape did sacrifice his life for Harry at the Battle of Hogwarts.
He was a double agent, so many character details were kept a secret. His mother was a witch and his father was a Muggle, leading to the moniker "The Half-Blood Prince."
Voldemort intentionally made six Horcruxes, but when he used Avada Kedavra on Harry, he unintentionally created a seventh Horcrux. Instead of dying, Lily's love for Harry created a counter 'curse' known as Sacrificial Protection and saved Harry.