Considering the lean part, the present paper adopts pull production and total productive maintenance, which are two well-known lean manufacturing techniques [28]. In this respect, pull production is enabled through ad hoc policies, such as Base Stock [29; 30], while total productive maintenance is integrated through predictive maintenance policies, e.g., condition-based maintenance, that seek to minimize maintenance costs and improve the availability of processing machines [31]. The implemented ad hoc policies are frequently employed in the real-world industry and the academic literature [32; 33]. On the other hand, the green manufacturing part is supported with circular economy policies, namely refurbishing and remanufacturing. These policies aim to minimize the environmental impact of products by extending their lifecycle [34]. In this respect, low-quality or returned material is processed again in order to create new and usable products. This leads to a substantial reduction in material consumption and raw material dependence. In terms of evaluation, the proposed mechanism is implemented in a multi-stage manufacturing system, influenced by degradation failures. The multi-stage manufacturing system is commonly integrated in the real-world industry. An example of such a system is provided as follows. Let us consider a manufacturing environment that manufactures gears. The gear manufacturing process involves two stages, that is, forming and machining. In the forming stage, the system procures raw materials. Thereafter, these materials are processed by the corresponding machine. This process involves activities, e.g., casting, sintering, extruding, etc., that create preforms of the gears. In this regard, each item completed during the first stage is called work-in-progress (WIP), since they are not in their final form. These WIP gears are stored in the inventory of the first machine until they are moved in the second stage, where the machining process is materialized. During this stage, the involved operations, e.g., milling, sharping, grinding, etc., complete the gears, forming their final characteristics, such as gear teeth. The final items are stored in the inventory before they are delivered to customers. Given the sophistication and robustness of such systems, a similar one is employed in the present paper. This system involves a two-stage manufacturing/remanufacturing process. In this context, the system can generate new items, or reform defective ones. Considering the behavior, the system is prone to a variety of random events impacting on its sustainability and flexibility in terms of quality and cost-effectiveness. The paper's objectives are summarized in the succeeding key points. Firstly, a degrading two-stage manufacturing/remanufacturing system prone to stochastic behavior is investigated. Both raw materials and returned products are considered as well. Secondly, a scheduling mechanism is formulated and presented in an attempt to jointly control and optimize the behavior and sustainability of the examined system through lean green manufacturing practices. This mechanism employs a RL algorithm and ad hoc policies. Using this implementation, the aim is to form combined scheduling policies of production, maintenance, remanufacturing, raw material procurement, and refurbishing operations, with the aim of formulating lean and sustainable production environments. Thirdly, simulation experiments are carried out to explore the proposed mechanism's functionality considering revenues, obtained costs, and output product quality. Furthermore, the effect of average activity rates on the manufacturing system's cost-effectiveness is investigated as well. The rest of this paper is organized as follows. Section 2 reviews the pertinent literature. The architecture and behavior of the system in question is summarized in Section 3. Section 4 details the presented methodology. Section 5 analyzes the efficiency of the proposed approach in terms of system profitability.