Is it permissible to use the remaining amount from academic stipends paid by the government for personal matters, or must it be returned?

If the state provides money for educational expenses, it is either a complete ownership based on the customary or estimated cost (with the actual expenses required to be stated), and any excess is yours. Or, it is a restricted ownership based on what was actually spent, in which case any surplus must be returned if proof of expenses is requested. This can be ascertained by referring to the granting authority, though the first type is more common. Honesty, trustworthiness, and fulfilling the contract are obligatory.