What is the ruling on the fluid that exits the vagina after purification from menstruation, and is not blood, and does it necessitate ghusl or wudu for every prayer, and what is required of someone who has prayed for many years with this fluid without knowledge of the ruling?

Yellow or brownish discharges during menstruation are considered menstrual blood; otherwise, they are not. If they are other than that, they are pure but invalidate wudu.

If the discharges are menstrual blood, there is no make-up for the prayers you missed during that period. However, if you prayed without performing ghusl after they stopped, then you must make up those prayers.

If the discharges are not menstrual blood, then you are obliged to pray. If they stopped for a time sufficient for purification and prayer, and you did not adhere to that, your prayer is invalid.

If the discharges are continuous, then your ruling is that of a woman with prolonged vaginal bleeding (istinadah): you perform wudu for each prayer after its time has entered. If you omit wudu, your prayer is invalid according to the majority of scholars.

Therefore, you must make up the missed prayers. If you do not know their number, then estimate and make up what you believe will clear your conscience.

Ibn Taymiyyah holds that whoever missed a prayer or a condition thereof out of ignorance is not required to make it up.