Is my Umrah valid with the discharge of a clear fluid mixed with a little yellowness after the Tawaf of Umrah? And is redoing Tawaf al-Ifadah due to feeling wetness correct, knowing that I do not know exactly when the wetness occurred? And are my prayers valid? And is it obligatory to remain in Mina until Maghrib or midnight on the last days of Tashreeq for those who did not hasten?

The tawaf of Umrah and Ifadah are valid. As long as the discharges occurred after completing the tawaf, they do not affect it. This yellowish discharge is not menstruation because it appeared after the usual time of your period. Your prayers are valid as long as you are not certain that any discharge came out after performing ablution. As for one who throws the Jamrat al-Aqaba al-Kubra on the third day of Tashreeq, he is not obligated to remain in Mina; rather, he is permitted to depart for Makkah.