Is it permissible to open an investment account through Tawaruq, based on the described steps which involve the client authorizing the bank to purchase a commodity and sell it to him, and then the bank selling the commodity to another party?

The transaction mentioned is reverse Tawarruq or reverse Murabaha. In this, the bank buys a commodity from the client at a profit, then the bank sells it to benefit from the money and repays it to the client in installments. The Islamic Fiqh Academy has issued a fatwa (definition) (religious edict) prohibiting this transaction.