Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
1) Please view this link for Aqaid of Ahlus Sunnah Wal Jama'ah (Adherents to the Sunnah and the Jama'ah i.e. Companions of the Messenger): http://www.central-mosque.com/aqeedah/tahawi.htm
Not having these Aqaid will either make one come out of the fold of Islam (i.e. Kafir) or from the Ahlus Sunnah Wal Jama'ah (i.e. become one of the deviant sect).
2) Yes, Ahl us-Sunnah Wal Jama'ah holds that the life of prophets in their graves is firmly established through authentic and explicit proofs.
please view this link: http://www.muftisays.com/qa/question/3208/state-of-our-prophet%28sm%29.html
And Only Allah Ta'ala Knows Best.