Is it obligatory to observe the proper sequence between missed and current prayers when performing the prayer while sitting in a vehicle without facing the Qibla, if there is sufficient time between the two prayers?

Combining prayers is specific to those that share a time, such as Dhuhr with Asr and Maghrib with Isha. The Hanbali school of thought dictates that there must be an order between the current prayer and missed prayers, except in cases where this requirement is waived. If you have missed prayers while traveling, begin by making up the missed prayers and then promptly pray the current prayer at the beginning of its time. It is permissible to pray in a car or similar vehicle for someone unable to dismount, and facing the Qiblah is obligatory. If the vehicle turns away from the Qiblah, you should reorient yourself towards it if possible; otherwise, pray in the direction the vehicle is facing.