Is believing in a statement about the unseen, which was introduced into a person's memory through hypnosis, considered an act of disbelief (kufr) or polytheism (shirk) that would result in the non-acceptance of prayers (salat) and supplications (du'a)? And what is its expiation?

The intrusive thoughts (waswasa) that afflict a Muslim do not lead to disbelief (kufr) and are not considered sinful. They do no harm as long as the heart is tranquil in faith and trusts in Allah. Merely speaking with some people about feeling regret over a sin is not considered an open declaration of it. A sound repentance is accepted and wipes away the effect of the sin, and the servant will not be punished for it in this world or in the hereafter. As for the relationship between a suitor and his fiancée before the marriage contract, he is a stranger to her, and he should not speak to her except out of necessity and for a legitimate purpose, while observing the Islamic guidelines.