Hard to say. Since technically it is not a medicine there are no well-studied guidelines to say the most appropriate dose. However, it is pretty safe, even in high doses. Some people do, indeed, report acne improvement with it.
Do better. Megadose pantothenic acid is probably safe enough though there anecdotes of bizarre side effects at the huge doses required; it may or may not help the acne. This is the 21st century and you have a right to something that actually works well & safely. I start with topical Clindamycin with or without a retinoic acid derivative, and move to systemic antibiotics as possible if needed.
Maybe. There have been studies done but to show benefit it required massive doses for prolonged periods of time and are not practical for regular use. It also showed some depletion of other b vitamins. Seek care from your dermatologist or medical esthetician for the best skin care advice on the best acne care available.
No. See a dermatologist. No vitamin is useful for acne. Oral Isotretinoin & topical tretinoin are in the same family as vitamina but are not vitamins.
Niacinamide. Topical vitamin b3 (niacinamide) is an effective treatment for acne.
No scientific. Studies behind it.
Unlikely. There are more effective, medically sound acne treatments. See your primary doctor or dermatologist for individualized treatment.
Worth a try. It's non-toxic though the doses recommended for acne will involve a lot of pills and nobody's done a real study and there are anecdotes of people getting sick from. Being 13 is hard enough without disfiguring acne, and junior has a right to effective treatment. I begin most folks with topical Clindamycin with or without a retinoic acid derivative, moving to stronger stuff as appropriate. Good luck.
Maybe. Skin health requires a concerted approach and in the case of nodulocystic acne requires use of medication. Healthy practices are: 1) reduced refined sugar, 2) elimination of food allergens, 3) supplementation with zinc and vitamin b5. There is some research to show that topical niacinamide is similar to topical clindamycin.