Well yes, he was in the Death Eaters but came back and joined Dumbledore. He never really was involved with Voldemort.
Not really. Does a spy really join the enemy lines? Severus was loyal to Dumbledore and the good side all the way along.
Yes, the dementors join Voldemort in Harry Potter and the Deathly Hallows.
Yes, Severus Snape was a spy. He was actually working to save Harry and bring down Voldemort.
Dumbledore sent him to try and convince them to join forces in the battle against Voldemort.
No! Peter Pettigrew told Voldemort where Lily and James Potter were. Then Voldemort asked them if they would join his gang, and they said no, Voldemort killed James, then told Lily to step aside while he killed Harry (their son). Lily refused, Voldemort killed her, and obviously used the avada kedavra curse on him (the killing curse). But it didn't work. Harry never died. That's why he's so famous. He's the boy who lived.
It's unspecified, but he was tortured by death eaters trying to find Harry.
Yes, the dementors join Voldemort in Harry Potter and the Deathly Hallows.
Voldemort always wanted to teach Defence Against the Dark Arts but Dumbledore refused to give him a job. Voldemort then cursed the position so nobody could hold it for more than one year. In the 1991/1992 school year he shared Professor Quirrel's body. Quirrel taught Defence Against the Dark Arts.
Yes, Severus Snape was a spy. He was actually working to save Harry and bring down Voldemort.
The wand recognised it's true master and left Voldemort's hand to join it's master.
Thanks to the incomplete prophecy told to him by Severus Snape, he believed that Harry Potter was the only one who could destroy him. Thus he went to the Potters' house, killed Lily and James, and then attempted to kill Harry. You know what happens after that.
Dumbledore sent him to try and convince them to join forces in the battle against Voldemort.
I do believe so, as the reason Dumbledore had Snape join the Order of the Phoenix and the Death Eaters was to relay information from Voldemort to the Order and the Order to Voldemort (usually fake information from the latter).
No! Peter Pettigrew told Voldemort where Lily and James Potter were. Then Voldemort asked them if they would join his gang, and they said no, Voldemort killed James, then told Lily to step aside while he killed Harry (their son). Lily refused, Voldemort killed her, and obviously used the avada kedavra curse on him (the killing curse). But it didn't work. Harry never died. That's why he's so famous. He's the boy who lived.
No,Ron Weasley never joins Voldemort's side. He becomes an Auror like Harry.
We don't know. It's possible that he had been forced to join the Dark Side, and then he had to do worse and worse things.
They don't. This only appears to happen in the movie and nothing in the movies should be considered canon because they are changed for dramatic effect.
At School. It says in Harry Potter and the Half Blood Prince when Harry and Dumbledore are going throught the memories. Alot of them were in the Slytherin House who WANTED to join him just for the glory of it.