Does the legal punishment for zina (fornication) – 80 lashes – apply to someone who fondled his fiancée, resulting in the emission of semen, knowing that he is remorseful and wishes for the punishment to be carried out on him?

What you have committed is considered treachery and sin. If there was no penetration of the glans into the vagina, then there is no hadd (prescribed punishment) for it. The obligation is sincere repentance, seeking forgiveness, and remorse. However, if penetration occurred, then this is zina (unlawful sexual intercourse) and the hadd must be applied if the matter reaches the ruler and the conditions are met. It is better for one who has been afflicted by this to conceal it with Allah's cover, and sincere repentance will suffice them. For Allah Almighty says: "Say, 'O My servants who have transgressed against themselves [by committing sins], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" [Az-Zumar: 53], and He, glorified be He, says: "And those who do not invoke with Allah another deity or kill the soul which Allah has forbidden them to kill, except by right, and do not commit unlawful sexual intercourse. And whoever does that will meet the consequences. Multiplied for him is the punishment on the Day of Resurrection, and he will abide therein humiliated. Except for those who repent, believe and do righteous deeds; for those, Allah will change their evil deeds into good ones. And ever is Allah Forgiving and Merciful." [Al-Furqan: 68-70]. And the Messenger of Allah, peace and blessings be upon him, said: "Whoever is afflicted by any of these abominations, let him conceal it with the cover of Allah." Repentance and seeking forgiveness are the religious rulings that atone for sin. Your fiancée must also offer sincere repentance. The flogging for an unmarried fornicator is one hundred lashes, not eighty, when the conditions are met.