Is studying considered an excuse for missing congregational prayers and Friday prayers, and for delaying prayers beyond their prescribed time, if it conflicts with university lectures that are essential for academic success, and if there is no other option for obtaining employment?

Congregational prayer is obligatory, but it is not obligatory to perform it in the mosque. It can be performed between lectures with colleagues. If that is not possible and you fear harm by leaving the lectures, then there is no sin in praying individually. As for Friday prayer, its matter is more emphasized, and one must be keen on it and not miss it except for a real excuse. If it is possible to attend lessons during the time of Friday prayer, even for a fee, then that is obligatory. If it is not possible to move to another place where studies do not conflict with Friday prayer, then do so. If all of that is impossible and you fear real harm by attending Friday prayer, then you have a dispensation to leave it and pray Dhuhr, provided that the harm is real and cannot be avoided.