.

Moreover, how does Stefan get deal with Cade?

There Kai learns that Stefan is human and attempts to kill him. Before he does he offers up some interesting information. Turns out when you kill Cade (The Devil) Hell also disappears. The two brothers gather Kai and the dagger and bring him back to the armory to hold him.

Secondly, how do you kill Cade Vampire Diaries? He finds Damon and psychically pulls Damon toward him, only to be stopped by Bonnie. As Bonnie has the same psychic power as Cade, she says she will fight for Damon. Bonnie is losing and Stefan plunges the bone dagger into Cade's chest, destroying Cade.

Regarding this, does Stefan kill Elena?

Much in the way Cade gave Damon a choice, he gave Stefan the same one: Kill 100 people or your brother's girl. And it seems Stefan chose to kill Elena. With that, Damon kills the first innocent person he sees, a visual that ensures Dorian will never choose life as a vampire.

Does Stefan become human?

Klaus later finds out and compels Stefan to kill her, but when he is able to resist the compulsion, Klaus makes him turn his humanity and emotions off. However, he is later able to get his humanity back, which is seen when he saves Klaus's life to protect Damon, but yet he pretends not to care about Elena anymore.