Q. 1. Can you tell me how a Catholic becomes a heretic because of a heresy?
A. 1. A heretic is one who persistently denies a Catholic doctrine in spite of reason and an explanation of the teaching. A heresy is the belief of the heretic who opposes the divinely revealed teaching of the Catholic Church.
Canon Law # 751 "Heresy is the obstinate denial or doubt, after baptism, of a truth which must be believed by divine and catholic faith."
A heretic cannot be ordained as a Catholic priest.
Canon Law # 1041 "The following persons are irregular for the reception of orders: 2° one who has committed the offence of apostasy, heresy or schism..."
Unless a heretic has renounced his errors before death, he cannot receive a Catholic funeral.
Canon Law # 1184 "§1 Church funeral rites are to be denied to the following, unless they gave some signs of repentance before death: 1° notorious apostates, heretics and schismatics;"
A heretic is automatically excommunicated from the Catholic Church without the necessity of he/she being informed of the excommunication.
Canon Law # 1364 "§1 An apostate from the faith, a heretic or a schismatic incurs a latae sententiae excommunication, without prejudice to the provision of Can. 194 §1, n. 2; a cleric, moreover, may be punished with the penalties mentioned in Can. 1336 §1, nn. 1, 2 and 3."