Is it permissible to purchase social-participatory housing in Algeria from a beneficiary before the lapse of five years from the contract date, knowing that the contract prohibits sale before this period, and the purchase is made via a general power of attorney that allows the buyer to dispose of the property after the period ends?

The ruler has the authority to restrict permissible matters, such as sales, if there is a clear public interest. Compliance with such restrictions is obligatory. Accordingly, neither you nor the beneficiary may sell this property before the specified period has elapsed, as Allah Almighty says: "O you who have believed, fulfill [all] contracts," and as the Prophet, peace and blessings be upon him, said: "Muslims are bound by their conditions."