I'll try and answer these quickly:
Originally Posted by Twist_of_Fate
When the Avra Kedavra Voldemort cast on baby Harry backfired, apparently a part of Voldy's soul stuck to Hary, making him a Horcrux. Yep, it was unintentional.
Harry finds out about this from Snape's final memories (As Snape's dying, memories pour from him and Harry views them in the Pensieve) and believes that to defeat Voldemort he must die as well specifically at Voldemort's hand to destroy the Horcrux. Harry comes to Voldemort for the final confrontation prepared to die. Voldemort casts Avra Kedavra on him, which destroys the Horcrux, but Harry doesn't die because they share the same blood (Book 4), the blood infused with the protection spell Lily cast.
This just destroys the Horcrux, Voldy actually dies when in the final confrontation Harry reveals that he is the true owner of the Elder wand Voldemort carries and the wand will not obey him. Voldy casts Avra Kedavra, Harry casts Expeliarmus. The Elder Wand flies from Voldy's hand, hitting him with the curse he just cast.
The best part of Molly killing Bellatrix is she actually calls he a bitch first.
As for Crabbe. He cast a magical fire in the Room of Hidden Things, trying to kill Harry and instead, it burns everything to a crisp, including the Ravenclaw's Diadem, which was a Horcrux. Crabbe also fails to escape the burning inferno, thus dying.