Is all installment-based transacting unlawful because it is not hand-to-hand, based on the saying of the Prophet Muhammad, may Allah’s prayers and peace be upon him: "If the types differ, then sell however you wish, if it is hand-to-hand"?

"The requirement for immediate possession at the contract مجلس العقد applies to usurious transactions when the items are of the same genus or علت, such as exchanging currencies or food items. However, this ruling does not apply to selling food for deferred payment (installments), nor to selling anything that is not of the same genus and lacks the same علت. Qadi Iyad mentioned that sales can occur on a cash basis or with deferred payment, and a difference in quantity is permissible unless the transaction involves currencies or staple foods."