What is the ruling on working in a place where prayer is not established, with no alternative available? Is it permissible to miss Fajr prayer in the mosque due to time constraints? And what is the ruling on abandoning the Qiyam (night prayer) of the last ten nights of Ramadan due to work?

If it is difficult to pray in the mosque due to work and not being allowed to leave, then there is no sin upon you. Pray at its legally prescribed time in your workplace, even if alone, because the prayer is valid and its validity does not depend on congregational prayer or being in the mosque. This is based on the Prophet's (peace and blessings be upon him) saying: "The earth has been made for me a place of prostration and a means of purification. So, any man from my Ummah whom the time of prayer overtakes, let him pray." Similarly, for Tarawih prayer, if it is difficult to go to the mosque, pray it even if only a few rak'ahs in your workplace during a break. Tarawih prayer is a confirmed Sunnah; whoever misses it misses its great reward but does not incur sin. If it is possible to take a leave during Ramadan to devote oneself to worship, that is better.