Retinol is a form of Vitamin A. It works by passing into your cells and binding to you DNA creating a smooth epidermis.

Start off once a week and maybe increase to twice a week to avoid a reaction. Once your skin is used to it you could increase to 4-5 nights a week. 

Please be aware you must use SPF daily while using this and you must stop using it for a couple of weeks before having waxing, microneedling and any skin peel. 

Cleanse skin first then apply at night, then apply your usual moisturiser at night. 

Start in your mid twenties onwards. This will help prevent fine lines, acne and hyperpigmentation. Retinoids incrase cell turnover and fade pigmentation. 

You can but not while your having an outbreak. 

Yes retinoid will unclog pores, reduce sebum production and exfoliate the skin. If your skin is red and sensitive you might get some flaking. Just start with once a week. 

I would suggest starting with tretinoin once a week