Al-jawab billahi at-taufeeq (the answer with Allah's guidance)
1) A person will not come out the fold of Islam but a person will be going against the teachings of the Quran.
Allah Most High says:
“It is not for the Prophet and those who believe to pray for the forgiveness of idolaters even though they may be near of kin after it has become clear that they are people of hell-fire.” (9: 113,114)
Allah Ta'ala says: "Ask forgiveness for them, or do not ask forgiveness for them! If you should ask forgiveness for them seventy times- never will Allah forgive them." (9:80)
The Messenger of Allah (Sallallahu Alaihi Wasallam) was prevented from praying for his uncle Abu Talib by Allah Most High. Similar was the case of Sayyiduna Ibrahim (Alaihis Salam).
It will be permissible to visit a non-Muslim to offer one’s condolences for a family bereavement. (Ahsanul Fataawa Vol. 4 Pg. 243)
It is stated in al-Fatawa al-Hindiyya:
“If a non-Muslim dies, one may say to the deceased’s father or some other relative of his: “May God recompense you with someone better and honour you with Islam, and that He bestow you with a Muslim child…” (al-Fatawa al-Hindiyya, 5/348)
Thus, it will be permitted to visit a non-Muslim in the event of a family bereavement.
2) Aqaid of Ahlus Sunnah Wal Jama'ah (Adherents to the Sunnah and the Jama'ah i.e. Companions of the Messenger), Please view this: 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).
Also, a person who renounces his/her faith will be Kafir and a person who deliberately immitates other religious belief such as, wearing the crucifix etc.
And Only Allah Ta'ala Knows Best.