Must one repeat the prayers that were shortened before travel or prayed while sitting on the bus due to ignorance of the ruling, given that their number is unknown?

The majority of scholars hold that a traveler should not shorten the prayer until he has left the houses of his village behind him. It is not permissible for him to shorten it while still in his town. This differs from some of the Tabi'in who permitted it merely upon the intention of travel. The majority cites the Almighty's saying: "And when you travel throughout the land, there is no blame upon you for shortening the prayer," [Quran 4:101]. Shortening is linked to traveling in the land (al-darb fi al-ard), and a resident is not called a traveler (darib).

As for performing the obligatory prayer sitting in the bus, it is valid if the worshiper fears falling when standing and is unable to perform it standing on the ground within its prescribed time. However, if he is able to stand in the bus or perform the prayer on the ground after disembarking, then his prayer is not valid; because standing is a pillar of the obligatory prayer that is only waived due to inability.