Is feigning ablution and prayer in front of one's parents, for fear of their discovering an act of adultery, considered hypocrisy that expels one from the religion?

What you are doing—committing adultery, abandoning prayer, and feigning prayer without ritual purity—are among the gravest transgressions and major sins that necessitate sincere repentance. Willfully abandoning a single prayer is more grievous than adultery, consuming alcohol, and taking a life. Some scholars even consider the one who abandons prayer to be a disbeliever. Furthermore, feigning prayer without ritual purity is also a major sin. Therefore, hasten to repent and desist from these abominations.