Thanks for taking out time to respond in details. Some of your answers showed that I did not really pay enough attention while reading. Concerning one of your answers

The hair growth stimulator may interfere with Dickkopf 2 (DKK2) and in the process hair follicles are automatically turned on thereby resulting in hair growth.

If hair growth stimulation is in areas where hair is totally lacking before, the above mechanism becomes plausible. However, it does not look the same in the case of someone that is just looking to speed up the hair growth process. For example, I have beards but it is not growing at a pace that I would have loved. Most ladies want longer hairs and as such, use stimulators. Sometimes, I consider the hair growth stimulator in the last case as mere placebo effect.

That leads me to another interesting question but I will perhaps seek the answer myself. How does hair transplant works? Take the case of balded Rooney for example.