Does God accept the repentance of the fornicator, what are its conditions, and how does a servant know that God has forgiven him?

Allah Almighty accepts the repentance of the repentant from any sin, including adultery, if it is sincere and genuine. Allah Almighty says: "Except for those who repent, believe, and do righteous deeds. For them, Allah will change their evil deeds into good ones." And the Prophet, peace and blessings be upon him, said: "The one who repents from a sin is like one who has no sin." Whoever has fallen into this abomination should not despair of Allah's mercy. Instead, they should turn to their Lord sincerely, with good expectations of Him, observe their obligatory duties, increase their supererogatory acts of worship, constantly remember Allah, accompany the righteous, and frequently ponder upon death.