Is money earned after graduation considered unlawful if the period of study included cheating in some subjects? And is a scholarship for a master's degree considered unlawful in this case? And does working remotely, without consistent attendance and with work being completed at irregular intervals, make the received wages unlawful?

If you regret and repent of the cheating you committed, then repentance expunges what came before it, and Allah accepts repentance from His servants. There is no blame upon you for completing your higher studies (Master's and others) and working with this degree if you are proficient in your work, and what you earn as a salary is considered lawful if you perform the work entrusted to you.