I'm 14 and I have minor bald spots on my head. Can I use a hair regrowth treatment to grow back hair in those bald spots?

Topical minoxidil is a FDA approved medication for hair growth.  It is relatively inexpensive.  Kaminomoto is marketed as a "hair tonic" for thinning hair.  It is not a medication and there is no evidence to support that it works.  It is a buyer beware market.  Use your...

You need an exam and a DIAGNOSIS of what you have / why you are losing hair.  If you know the cause, you can consider a treatment.  TRYING steroid injections for what? You need to have more understanding and clarification from your doctor.  

Yes, you can use hair serum without minoxidil but it probably will not work to grow hair.  The main active ingredient in these serum that grows hair, is minoxidil.  If you take out the main ingredient, what is the point?

There are only two medications that is proven to grow hair.  These two medications are: (1) topical minoxidil (2) oral finasteride.  If you stop using minoxidil then whatever hairs you gains from using minoxidil will be lost.

In general genetic male pattern balding is not a condition which you can reverse or completely stop.  In general there are medical treatment options such as Propecia or Rogaine that can slow the process down.  You should follow up with your doctor.

It seems you have seen many doctors and have a treatment regimen.  There really isn't much more "out there" in terms of treatment.  The best course of action is to find a good doctor and stick with the treatment and follow up with the doctor if the treatment does not work....