If you have oily skin and acne problem, sometimes if acne is severe they might burst or get infected or if you pick your acne too much they might result into scars. As per Dermatologist there are 5 types of scars which are commonly encountered. 
1. Ice Picks Scars: Very small in surface but deep and narrow below. 
2. Roll-Over Scars: Wide but borders are difficult to appreciate 
3. Box-car Scars: wide and borders can be easily appreciated. 
4. Open pores like Scars: Small Ice Pick Scars 
5. Hyper-trophic Scars: 
so the treatment for the scars depends upon the type of scars. Commonly treatment which are effective are TCA cross, subsition treatment, microneedling, microneedling radiofrequency, PRP treatment, CO2 Laser, RBM Glass laser and even dermal fillers. 
As you are 23 and you are asking about microdermabrasion, it removes superficial skin layers and it is effective only for superficial scars which are not very deep. This might require you multiple sessions like 8-10 sessions for it to work. Instead of Microdermabrasion you can go for microneedling, microneedling radiofrequency which will require less number of sessions and on top of it you can add PRP to it.

Micro-needling Dermabrasion or crystal microdermabrasion somewhat work as wrinkle treatment, but it wont result in dark circle improvement.

For very big open pores, the oil secretion needs to be controlled, because if oil secretion is not controlled, the pores wont reduce. For oil correction using salicylic acid based face washes, avoiding hair oil are important measures. Apart from that micro-needling or micro-needling radiofrequency, CO2 Laser are better options than just dermabrasion though microdermabrasion might have little effect on open pores.

Purple or bluish discoloration may be because of less oxygen or irritant or allergic contact Dermatitis... You need to consult dermatologist for detailed examination also

Dandruff is a fungal infection and there is not permanent cure for dandruff.

Dermatomyositis is a multi-system inflammatory disease which is auto-immune in nature. Though the rashes or skin liaison will be treated by the dermatologist. The management of Dermatomyositis involves multiple physicians like general physician, Rheumatologist and dermatologist. It has to be controlled with the immune suppressants and the symptomatic treatment. Sun protection is important for dermatomyositis

For recent onset acne at the age of 20 yrs. It is recommended to stop applying hair oil and use salicylic acid based facewash for face and gel containing clindamycin should be applied morning and evening. Topical retinoids can be applied at night. If acne doesn't clear with this you can consult dermatologist and also it is important to continue the treatment for longer time otherwise there are chances to reoccur after stopping the treatment.

If its only acne marks, continuing your acne treatment with facewash and gels will improve it. Some topical agents also helps in removing the pigmentation and marks of the acne. Even Salic acid 20% gel at night on spots is helpful. Glyco 6 or Glycolic acid 6% is recommended for application on the face. Acne compatible sunscreen is also helpful. Chemical Peeling with glycolic acid or salicylic acid is useful

By Padar Fungal infection it looks like you are talking about fungal infection of the foot which might present with the flaky or itchy sole. Generally it is more on one feet or just affecting one feet. If it is affecting both feet then its asymmetrical. The treatment is you have to wear less of shoes so that sweating is less. Open footwear is most preferable. Topical and oral antifungals is the mainstay treatment but if nail is also involved then treatment has to be taken for the long time so that the reserve side of the infection is treated. Consult a dermatologist for proper consultation.

If the hairs are falling from front at the age of 11 years that might be due to tractional alopecia or very tight tying of hair. There should be loose or normal tying of hairs. It is always better to consult a dermatologist for proper diagnosis and treatment.

Acne is multi-factorial problem, hormonal disease in most of the patients, diet, exercise, hygiene, grooming practices play important role.so visiting dermatologist and taking treatment is one option and maintain treatment for long time because if you are getting any improvement with the treatment then continue it otherwise dermatologist will change it. there are few things that has to be taken care. One thing not to apply hair oil, avoid having dandruff or use anti-dandruff shampoos weekly on the scalp, using face washes that have salicylic acid or glycolic acid. Avoid using thick greasy moisturizers or cream on the face. Use only creams that are gel based or water based. Drink plenty of water, avoid fat or cheesy diet, exercise 10-15 mins of the day. Topical steroids have to be avoided. Topical antibiotics like Clindamycin are useful. Oral Antibiotics or retinoids are advised. 

There is no as such any best treatment for eczema, but a good moisturizer and keeping the skin away from the allergens will keep you away from eczema 

There is no permanent cure for acne. acne is the continuous process because of the oil glands in the skin that are more sensitive and reacting to the hormones in your body that might fluctuate or might be in abnormal quantity, that result in more oil secretion on the seborrheic areas like face and chest, that is resulting in bumps or impulse. If you are getting relief by the treatment, you have to continue some sort of treatment even after acne is gone like no oiling of the face, use anti dandruff shampoos, use salicylic facewash, avoid using thick creams, use topical agent for management of acne, increase water intake, avoid high calorie diet and exercise regularly.