Is it permissible to demand the money I gave to my former fiancé as a debt, considering he has not returned it after six years since the engagement was dissolved?

If the man refused to take the amount except as a loan, he must repay it, and the woman may demand it through lawful means if he is able to pay and refuses. However, if he settles on accepting it as a gift, it is not permissible to demand it back, based on the Prophet's (peace be upon him) saying: "The one who takes back his gift is like a dog that returns to its vomit."