1. What does keratin do exactly?
Your Questions Answered: No. 1: What is a keratin hair treatment?, The Facts About Keratin Hair Treatments

2. Is it permanent? If not, how long does it last, and does your hair revert back to its original state?
It is not permanent. My hair was back to normal after about 4 months.

3. Does it straighten your hair completely or can you choose how you want it to look? I have 3c hair and I would like looser curls, not straight hair.
It did not straighten my hair at all, it made my curls looser. I don't flatiron my hair very often but the time I did it went fast.

4. Does Keratin damage your hair?
I've read that some people have had damage, I'm not one of them.

5. Do Keratin conditioning treatments (like shampoos/conditioners with keratin as an ingredient) give you the same results as the ones you get in a salon?
I've never tried at home treatments..

6. Have you tried any Keratin treatments, and were you satisfied? If so, which treatments would you recommend?
1½ years ago I did a Brazilian Blowout Free (no formaldehyde) on my 4a/3c/3b/3z hair.
It made my curls looser and a litte more uniform.
Having done research, I asked my stylist to NOT flatiron each piece 10 times so she only went over it 5 times.
I swear by the aftercare, shampoo, conditioner and leavein.
I'm not sure what is the cause but my length retention has been great.

I recently stopped using the aftercare because it's been impossible to find around here. My hair felt brittle and dry so i decided to do a BB again.
Unfortunately my stylist is no longer using BB. A lot of customers felt that the BB Zero was to weak, I assume they wanted stick straight hair, so she is now using Kebelo. I've had it a week, my curls are a little too loose but I know that it will wash out eventually and I just want the protein-retention effect anyway.

I found my beloved BB Zero aftercare products again so here's hoping.