I am a 28-year-old woman. The skin over my elbows is very dark and rough. I also wear heavy jewellery and have recently started noticing that the skin around the nape of my neck has become very dark. Can you please advise me a cure for this problem?
The skin over the elbows is subject to a lot of friction and stretching because of joint movements. Therefore, it tends to be thick, rough and dry. Avoid constant friction. Keep your elbows moist by regularly massaging them with nourishing creams, which are rich in AHA and Vitamin E. Regularly massaging your elbows with granulated sugar and lime juice will also make them soft and light complexioned. Pumpkin and papaya packs are also good for softening the skin.  Roughening and darkening of skin around the neck is generally due sensitivity to metals in the jewellery or perfumes used around the neck area. It can also be due to being overweight or diabetic. Avoid artificial jewellery and perfumes which you may be allergic to. Check your weight and get yourself checked for blood sugar.
From your above listed problems it looks like you are prone to pigmentation and it is developing all over your body. There are several reasons for pigmentation, like hormonal changes, over sensitivity to sun exposure, being over weight, reaction to some wrong products, constant friction of the specific body part, etc. Observe your daily pattern and try and check for any of the above. If you think it has started after the use of some new product or some change in your lifestyle stop that immediately. Use sunscreen on all the exposed areas while going out in the sun. Avoid using highly perfumed soaps, creams and deodorants etc. You can use AHA creams and de-pigmentation creams over the problem areas and it should help in clearing pigmentation. If problem persists after having taken all these precautions consult a dermatologist immediately before the problem gets aggravated. Advanced treatments like Micro Dermabrasion, Intense Pulse Light (IPL)-used with different filters for specific problem area, fruit acid peels, skin lightening massages etc. should work very well in clearing your pigmentation. 

I am a 15-year-old girl. I have clear skin but am developing small white boils on my cheeks. I have tried to squeeze them out but it hasn’t helped. How do I get rid of this problem?
You seem to be having whiteheads on your cheek area. They are deposition of protein called Keratin in closed pores. These appear as white shiny globules or dots over the skin. Unlike blackheads, which are present in open pores and can be removed easily, white heads cannot be squeezed or pressed out. Please don’t try to pinch them out because you may end up scarring your skin very badly. You should consult a dermatologist. Keep your face clean and use a mild exfoliating pack regularly.