Faraaidh of wudhu

Q: I am a Muslim woman and have a permanently damaged toenail due to trauma. Although it is not causing physical problems, the appearance of the nail causes me significant embarrassment and distress and affects my confidence. 

I am getting married soon and would like to know whether it is permissible to use a cosmetic toenail reconstruction or similar treatment to restore the appearance of the damaged nail. My intention is not simply beautification, but to conceal and correct a defect that resulted from injury and that causes me considerable emotional distress. 

If such a treatment forms a layer over the nail, how would this affect the validity of wudu? Is there any allowance in this situation, or would it need to be removed for wudu?

Q: I put a plaster on the back of my mother's foot at around isha as she had a blister. She still had it on until the next day Maghrib because she forgot about it. Are her prayers invalid?

Q: From my understanding, the hair transplant treatment is permissible. After having it done, one is required not to let water touch the scalp for about 3 days. How then should one do masah?

Q: Is it necessary to rub the eyes when making wudhu?  If a little dirt is stuck in the corner of the eye, is wudhu accepted?

Q: Will my wudhu or ghusal be accepted if I have instant henna/mendhi on my hands. If not, why?

Q: I am a mechanic and work with grease. Often the grease gets stuck to my hands and cannot be removed by any means and only comes out after many hours. How should I perform wudhu and perform salaah?

Q: A scholar mentioned that it is fardh (obligatory) for two drops of water to fall from every hair and part of the skin that must be washed in wuḍūʾ. If this does not occur, it will be considered as masah (wiping) rather than proper washing. However, another scholar stated that as long as two drops of water fall from the entire limb, the wuḍūʾ will be valid, and it will be considered as washed. Which of these opinions is correct according to the Sharīʿah? 

Q: If a person is physically unable to lift his feet to wash them in the basin, is it permissible for him to perform masah (wiping) over the feet instead of washing? 

In such a case, if Ṣalāh is performed after doing masah instead of washing the feet, does the Ṣalāh need to be repeated?

Q: 

1. If wuḍuʾ is performed using a spray bottle, is the wuḍuʾ valid? 

2. With regard to the obligatory (farḍ) parts of the body that must be washed in wuḍuʾ, is it necessary for two drops of water to fall from each hair and part of the skin, or is it sufficient for two drops to fall from the entire organ (e.g., the face), even if only two drops fall in total after spraying water?