Task labor law

At the checkpoint of the plant, it became necessary to replace the equipment that provides control and accounting for the time of arrival at work and departure from the plant of workers and employees. It was decided to carry out these works on weekends (Saturday and Sunday). To do this, the plant hired a group of specialists, including plant workers, with whom a labor agreement was concluded. Its content specifically stipulated the following conditions: a) the final result of the work; b) working time (term); c) the total amount of remuneration of the group, indicating the specific amount received by each performer.
After completing the contractual work and receiving the calculation, the plant employees (members of the group with whom the labor agreement was concluded) applied to the plant director with a statement. They asked the head of the organization to pay them overtime (Article 99 of the Labor Code of the Russian Federation), as well as provide other days of rest instead of Saturday and Sunday (Article 112 of the Labor Code of the Russian Federation). The specialists motivated their demand by the fact that on Friday the group worked after the end of their shift, and on Saturday and Sunday they worked only with breaks for eating and short rest at the place of work, which did not exceed 4 hours a day. It was this mode of work that allowed the group to fulfill the terms of the labor agreement.
Are the demands of the factory workers justified? Are the relations of the members of the group who have entered into an employment agreement with the plant, labor relations?