No, not before his death in any case.
Note: Nobody knows, not even himself... he has changed sides, but he did not become good.
snape particpated in the battle of hogwarts and was killed by lord volodmort because snape was rumored to be the true master of the elder wand and like dumbledore when he killed had a portait of him in his office they decided to do the same for snape
JK Rowling has, as of yet, never stated who became headteacher at Hogwarts after McGonagall. All we know is that McGonagall had retired by 2017.
Snape refers to Harry as Hogwarts new celebrity. He then goes on to drill Harry about important Potions knowledge that Harry doesn't know.
Severus. I know a song Snape Snape Severus Snape! Found it online
Voldemort didn't know Snape had changed sides, Snape was a spy.
Snape was an accomplished Occlumens.
snape made a unbrackable vow to Draco malfoys mother and by doing so swore to do anything in his power to help Draco, Draco's mission was to lead the death eaters into hogwarts and Draco himself must kill dumboldore, he found he could not kill him so snape killed him for Draco. Actually, Snape had already promised Dumbledore that he would kill him, for Dumbledore was already dying, so instead of having Draco ( who has never killed anyone) have this sin on his hands, dumbledore had pre-decied that snape would be the one to kill him. Snape was dumbledores man through and through so there was no way that if dumbledore had not had asked snape to kill him, snape would never have gone through with the unbreakable vow. Dumbledore was always steps ahead of everyone and know that his death was coming, so he choose the time and manner of his death.
In the second book when Dumbledore has to leave for a while she steps up to the plate. Dumbledore comes back and is headmaster until he gets killed by Snape and again she becomes headmaster.
Do you really want to know without reading it first. Or are you waiting for the movie. If you want to spoil it ok Snape does. But Snape is also a good guy. So I won't tell you why he did. You have to wait until Number 7 for that one. If you want to know read it.
Since Hogwarts is a fictional school, nobody can attend it.
Easy, muggles cannot see Hogwarts so he did not know it was there. Because Hogwarts is an imaginary place that doesn't exist in reality.
Snape was a student at Hogwarts along with James Potter, Sirius Black, Remus Lupin, Peter Pettigrew and Lily Evans (to name a few significant others in the story). Whether or not Hogwarts was under the ruling of Albus Dumbledore or not I am unsure however if Dumbledore was not headmaster then I can assure you that he was a professor at the school. Later when he left school, Snape became a Potions master at Hogwarts. He had a deep love for Lily Potter (nee Evans - Harry's Mother) and a deep hatred for James Potter (Harry's Father). When he became potions master I am positive the school was under the ruling of Albus Dumbledore. The two became closer than some of the other teachers at the school largely due to Snape's learning of Voldemort's plans with the Potter family. Snape went to Dumbledore to seek protection for Lily - reluctantly giving in to protection for the three Potters, one of which he hated and one of which he didn't know. Snape was then angry when the protection provided did not end up being enough and the love of his life died. Snape also played an important part in the whole plot. He was Dumbledore's assistant, of sorts. He was meant to kill Dumbledore to ensure the safety of the Elder Wand. He was also a part of the Order, an organisation of sorts that Dumbledore set up to plot against Voldemort. He was enlisted to deliver the sword to Harry and to tell Harry the truth when the time came. In short (though this is a very confusing subject to describe in a nutshell) Snape was a student and then teacher under the ruling of Albus Dumbledore, and the two became rather close.