Is the yellow fluid that came down before the menstrual period with cramps, without any blood coming down after it, considered menstruation, and must the prayers performed after its discharge without performing ghusl be repeated?

Since you saw this fluid outside of the period of your regular menses, it is not considered menstruation according to the preponderant opinion. Moreover, it appears that it did not last for a full day and night, which is the minimum duration of menstruation according to the majority of scholars. Therefore, your action of not performing ghusl (ritual bath) and continuing to pray is correct, and there is no blame upon you for it. You are not required to make up any prayers.