Try our 0.1% Tretinoin cream on your hyperpigmented scar. Tretinoin improves hyperpigmentation but you have to apply it long term.
A cream with hydroquinone should also help.
For your shallow scars on the cheeks and the lines around the mouth, buy a 1 mm or a 1.5 mm dermastamp. Do a test patch first to see whether your skin ends up hyperpigmented. Redness for many days after stamping is completely normal though.
If you have the rolling type of acne scars and you get no results with just stamping, add the suction method:
https://http://forums.owndoc.com/dermarolling-microneedling/subcision-suction-method-for-acne-scars/If your skin reacts OK to stamping, you can try to stamp your forehead scar to make it smoother but do not perform any aggressive stamping. Start very slowly on a small part of the scar to see what happens.
No, a dermaroller will not help with dry, flaky skin.
Dry skin is not caused by lack of water - it is caused by excessive evaporation of water from the skin. The natural skin barrier that should prevent evaporation doesn't work properly. Supplying dry skin with hydrating creams doesn't work. It needs some fats to keep the moisture in. In fact, hydrating creams saturate the skin surface with water which makes the skin look temporarily better but this very temporary hydration actually increases the evaporation of water from the skin! Adding water does not solve dry skin. Establishing a barrier that prevents water evaporation solves it. That is why oils are much better moisturizers than any light moisturizing cream because oils form a film on the skin that prevents the evaporation of water.
The film however can be a problem with acne-prone skin.
I use almond oil to clean and moisturize my skin. I slightly wet a cotton pad with tap water, add almond oil and clean my face. Almond oil will keep the skin moist and supple by preventing the evaporation of water from the skin. I also apply almond oil on my body (while the skin is still wet) after a bath. I keep a bottle of almond oil in the fridge and refill a small container that I keep in the bathroom. From time to time I use fine salt in the shower for exfoliation but do not exfoliate too frequently.