I've never heard of Keto being used to fight or prevent acne, nor Keto causing acne. The only side effect I had was headaches and lack of energy. I learned the headaches were normal for the first few days as the body adjusts to burning ketones(fat) instead of carbs. The low energy was due to me not eating enough good fats..
It usually takes a few days to see any changes, as the body will burn all available carbs and glucose before making the switch to ketones for energy.
As for when to carb-up, that is user-decided, as opposed to a set standard. I think most people go with a carb refeed every week, for an 18-36 hour period. I first read of Keto and people going a full 10 days without taking in significant carbs, then having a refeed. Using that method means you'll have to rework your gym schedule to stay in line with the refeed, if you wanted to. The once-a-week refeed is much easier to manage and set timing on, so a lot of people have been using that type of cycle.
Mt Snow, VT - May 5, 2012 - Completed!
Gunstock, NH - June 1, 2013 - Completed!
...i remain, he who remains to be...