Does committing unlawful acts, such as backbiting, gossip, and mockery, invalidate and prevent the remembrance of Allah and acts of worship like ablution, reading the Qur'an, and charity? And are these acts causes for a decrease in religiosity, the devil's deception, and hardness of heart?

Sins do not prevent acts of worship, but they can invalidate the reward of good deeds and stand between a person and goodness. The servant must repent of sins and strive in obedience. The reasons for little religiosity and the delusion of Shaytan are heedlessness of the remembrance of Allah and love of the worldly life, negligence in fulfilling obligations and supererogatory acts, procrastination in repentance, and following one's whims. Salvation is achieved by holding fast to Allah, striving against one's soul, increasing in the remembrance of Allah, and contemplating the Hereafter.