I am a disabled woman who has vaginal discharges and can`t control her urine. Therefore, I combine prayers. Is that permissible?

All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all his family and companions.

According to the Hanbali doctrine, it is permissible for the sick to combine prayers. In your case (Asker), it is better that you delay the noon prayer until a few minutes before the afternoon prayer in order to minimize the time span between the two and perform each alone. In addition, you can do the same with sunset and evening prayers. Finally, we ask Allah to bless you with recovery. And Allah Knows Best.

What should a person, who delayed making up missed fasts of last Ramadan due to the continuance of the same excuse, do?

It is permissible for one, whose excuse for not making up missed fasts of last Ramadhaan has continued, to delay fasting until the excuse ceases to exist, and he is considered neither sinful, nor obligated to pay a ransom. And Allah Knows Best.

Is it permissible to single out Fridays, Saturdays, and Sundays to make up for missed fasting without fasting a day before ,or after each ?

Yes, it is permissible to make up for missed fasting during the aforesaid days, and it is also valid to offer non-obligatory and vowed fasting as well. However, fasting a day before or after each isn`t obligatory. And Allah Knows Best.

Does bleeding from the body, such as from wounds, invalidate ablution?

Bleeding doesn't invalidate person's ablution. And Allah Knows Best.