Does bleeding from the body, such as from wounds, invalidate ablution?
Bleeding doesn't invalidate person's ablution. And Allah Knows Best.
What is the ruling on the yellow discharge that comes from a woman during pregnancy?
These discharges are not menstrual blood, but they are impure like urine and break the Wudu (ablution). If the discharge is frequent, its ruling is similar to that of urinary incontinence. The woman should perform wudu after the time of each prayer, pray the obligatory prayer, and any additional prayers she wishes, read the Quran, and take precautions against impurity to the best of her ability. Using a special pad can prevent the impurity from spreading. And Allah Knows Best.
Is the marriage, which lacks a valid legal contract, a guardian, and a court registration, valid?
It is incumbent that a valid marriage contract be concluded in the presence of a guardian and two trustful witnesses, and it should be registered in the court to protect the rights of the wife. Actually, a valid marriage contract is what differentiates between sound marriage and fornication.
Is the son of the sister by breastfeeding considered a mahram in Islam, and is it permissible for a woman to go for Hajj with him?
Everything that is prohibited by lineage is also prohibited by breastfeeding. The son of the sister by breastfeeding is considered a mahram, just like the son of the sister by blood, and it is permissible for him to be her mahram for Hajj and Umrah. And Allah Knows Best.