Is zakat obligatory on an amount saved from a study allowance, knowing that a large part of it is a loan to relatives, and is zakat obligatory for previous years?

It is necessary to know when the money reached the nisab (approx. 85 grams of gold or 595 grams of silver), and its zakat becomes due after one full hijri year has passed over it without it decreasing below the nisab.

Money saved during the year is acquired wealth, and its zakat becomes due when its year (the hawl) is completed. Alternatively, its zakat can be paid in advance along with the zakat of the original capital, according to the majority of scholars.

There is no zakat on what was spent during the year.

Zakat is due on money lent out. It can be paid along with the original money, or its zakat can be paid for previous years.

The zakat for all past years in which the money reached the nisab must be paid, because it is a debt owed.