What is the ruling on the prayer of a traveler who shortened and combined prayers for the first three days of his journey, then completed them, and does he only have to make up the four-rak'ah prayers or all of them?

The lawful journey that permits shortening prayers (qasr), combining them (jam‘), and breaking the fast in Ramadan is not determined by duration but by distance, which is four buruds (approximately 83 kilometers). Whoever travels this distance is recommended to shorten the four-rak‘ah prayers and is permitted to combine them. If one completes their prayers, they are valid, but they miss the sunnah of qasr, and there is no obligation to make them up.