What is the ruling on shortening and combining prayers for a traveler who moves between different cities and stays for several days in each, and what is the ruling on Witr prayer with the combined prayers?

There is no blame upon you in shortening and combining prayers, as long as you do not intend a stay that severs the ruling of travel, which is four days exclusive of the days of entry and exit. There is no blame in praying Witr after the 'Isha prayer, which is combined with Maghrib in advance (jama' taqdim), because the time of Witr is linked to the 'Isha prayer, not to the entry of its time. This is the view of the Hanbalis and Shafi'is. As for the Malikis, they hold that the beginning of Witr's time is after the valid 'Isha prayer and the disappearance of the twilight, so Witr should not be prayed with jama' taqdim until after the disappearance of the twilight.