Faraaidh and Sunnats of ghusal

Q: There is a device on the market which is attached to the skin. It gives you a continuous and real time reading of your blood sugar levels by which a diabetes patient will know when to take his insulin and how much insulin he should take. (Not over or under administering the medication) 

The device is quite expensive (removing & changing the device each time you require a farz ghusal will be very costly). The device has an adhesive tape by which it is attached to the skin thus preventing water from reaching underneath it. Will the farz ghusal of a person wearing such a device be valid if he makes masah only over the device and washes the rest of the body?

Q: I have issues with my ghusl concerning the validity of it due to specific barriers. 

I scrub my ears yet there is still some sort of wax at the part that curves. I sometimes scrub so hard it scabs. 

I also have some white patches in the middle of my chest. I’m not sure what it is but I also need to scrub hard for it to be removed. 

I have an ear piercing hole, how do I clean inside of it, if it’s closed but sometimes some sort of sebum comes out when I rub my piercing hole which is pretty much shut. I have some hard dirt on/in my bellybutton. It is extremely hard to remove as it’s engraved in the grooves of my skin.

Lastly I have an eye issue called blepharitis where dandruff like flakes are on my eyelash and eyelid. Sometimes I finish my ghusl and see these flakes/crust on my eyelid and lash. Are the things mentioned barriers for my ghusl?

Q: My wife has nail polish with artificial nails. After we had relations, she wanted to make ghusl, but the nail polish and artificial nails are not easy to remove. It may harm her natural nails. We are on a journey and it is not easy to get removing facilities. Without removing the nail polish, is it permissible to make ghusl or not?

Q: Many women say that they only wet the scalp of the hair after relations due to the hadeeth of Sayyidah Ayesha (radhiyallahu anha). Is this correct? 

Q: I have some skin tags on my face and shoulders. In order to remove them I tie dental floss tightly around it because it's flat. Regular cotton is sharp and cuts through it. The tags fall of after 10 days or so.

Will my fard ghusal be done while the dental floss is wrapped around the skin tag.

Q: If I forgot to say Bismillah before doing ritual bath, is my ghusl valid? Is Bismillah mandatory before ghusl?

Q: I had cataract surgery on one eye. The doctor advised not to let water go into the eye that has been operated on. How do I make ghusul for jumuah?

Q: Does earwax in ears prevent water reaching in the ears, or is it ignorable and doesn't prevent validity of ghusl?

Q: I took a bath after haidh forgetting that there is nail paint on my one nail. What should I do now? Can I peform wudu or should I take a bath again although my hair is wet?

Q: Is taking a bath in a bathtub haram? Does it resemble the kuffar or because of the usage of water is too high as compare to taking a bath with a bucket and much or compare to using shower. So will it be israaf?