Is it permissible to borrow money from a younger sister to complete university studies, with a commitment to repay it later? And what is the ruling on tears and mucus flowing from the nose when hearing the Qur’an, and how can one get rid of this problem?

It is not permissible to dispose of the property of a young, minor sister except in ways that benefit and preserve it. The person who decides this is her guardian (her father, if he exists). It is not permissible for the person responsible for her property (the guardian or executor) to donate anything from it, nor is it permissible for him to spend from it on himself or on those whose maintenance is incumbent upon him, unless he is poor and in need, in which case he may take according to his need. Therefore, what the brothers proposed is not permissible to do, and the property of the minor sister must be preserved until she reaches the age of maturity and it is handed over to her.