Is it permissible to disobey a mother who compels her son to study abroad, given the prevalence of sins and temptations there, and his desire to return to a Muslim country for worship and to focus on the hereafter?

The right of the mother is great, and honoring her is emphasized. However, obedience to parents is obligatory only in what is good and permissible, and it does not include doing what harms one's religion. If the child fears temptation in his religion in the lands of disbelief, then emigration from them becomes obligatory for him, even if his mother does not approve. If it is possible to convince her first, that is preferable, to preserve one's religion and the mother's رضا (satisfaction/pleasure). But if she becomes angry, there is no sin upon the child, and that is not considered an act of disobedience.