Factors that break wudhu

Q: I was sitting after performing salaah when I noticed that there is a black, sticky substance on my foot through which water could not pass. It was the size of a whole round fingernail, and I had not seen it before.

Then, my brother told me that he saw it since 3 or 4 days on my foot. I had also led jamaat during these days. Will I have to repeat all the salaah that I had offered on these days? Will those who followed me in jamaat also have to repeat their salaah?

Q:

1. Is it necessary to make wudhu for each salaah if one has discharge randomly throughout the day?

2. If one salaah was read and by the next salaah time there is no discharge seen nor felt, is it necessary to make wudhu?

Q: When I test my blood sugar, after the prick, the blood does not come out on it's own. I have to squeeze my finger to make the blood come out. Does my wudhu break through this?

Q: If one has oil in their hair and performs wudhu, is the wudhu valid?

Q: If a woman puts a tissue paper in her vagina and see that the tissue paper is wet (probably due to the moisture found in the lips of vagina), will wudhu break? Is this also a type of vaginal discharge? 

Q: I see discharge only in the inner labia and it is there always but the outer side is always dry. Is my wudhu valid?

Q: Does mucus that comes out of the eyes break one’s wudhu?

Q: I used something called a douche... I insert it with liquid medication and insert it into my private part and wash myself out. Thereafter I make wudhu. When I come out of the shower, some of the water comes out from my private part. Is my wudhu still valid?

Q: I am a 30 year old newly married male. When I touch or kiss my wife, a little amount of semen comes out. In this condition can I perform namaz by washing the affected area without changing clothes or underwear?

Q: I would like to know if ghusl is fardh on a woman if she has a thought and feels a slight discharge, but doesn't check it because on every ocassion it is seen to be normal discharge, and not mani.

I always experience this during istinja and have checked on many ocassions, but have recently stopped checking because I experience a lot of normal discharge and know it can't be mani. I am still doubtful. Am I ritually impure for not checking this time?