Summary
- The Resurrection Stone did not bring Harry back to life because it cannot fully restore the dead to life, as shown in "The Tale of the Three Brothers."
- Voldemort being a Horcrux for Harry is unlikely because creating a Horcrux requires splitting one's soul through murder.
- Harry survived the second killing curse because a piece of Voldemort's soul lived inside him, and when Voldemort cast the curse, it only killed the piece of his soul inside Harry. Harry's connection with Voldemort helped him time and time again, including surviving the killing curse for the second time.