What is the ruling on purchasing in installments from stores that deal with banks as intermediaries, where the bank pays the full price to the store and collects the amount from the buyer in installments without interest? And what is the ruling on that if purchasing in installments leads to an increase in price?

If the sale truly occurs between the buyer and the store at a specified price, and the buyer pays the price to the bank in installments without any increase, then this is permissible. However, if the bank pays the price to the store and then collects it from the buyer with an increase in installments, then this is a prohibited usurious transaction.