Is it permissible to pray Fajr and Dhuhr before the time of Fajr prayer for someone who leaves before Fajr and returns after Asr, and is prevented from praying during working hours?

It is not permissible to pray Fajr and Dhuhr before their appointed times. One of the conditions for the validity of prayer is the arrival of its time. Whoever prays before the time, their prayer is invalid, and they must repeat it after the time has entered. There is no difference in this matter between Muslim countries and non-Muslim countries. If a Muslim knows they will be prevented from praying, then it is not permissible for them to join such a course.