Is it permissible to subscribe to an e-commerce application where the user pays a certain amount, then performs daily tasks such as reposting product reviews (marketing) to receive a pre-determined sum of money, with the full amount paid being refunded after two months, knowing that the website is guaranteed?

The described transaction can be characterized as a lease (ijarah), but the condition of depositing a guaranteed sum to be returned at the end of the contract is considered a stipulation of a loan within a lease contract. It is not permissible to combine a loan with any compensatory contract, such as a sale or a lease, because the Prophet (peace be upon him) forbade combining a loan and a sale, as it serves as a means to usury, given that a loan benefits its lender. Every donation combined with a sale or a lease is in the same حكم (ruling) as a loan, so a compensatory contract and a donation should not be combined.