There's a small mole on my forehead below my hairline and I heard ACV helps to remove it is that safe and is it 100% satisfied?

You should absolutely not try to remove a mole by yourself with apple cider vinegar.  This treatment can cause harm, but it should not go into your brain and kill you.  The safest method to remove a mole is by going to a physician to do so.  A facial plastic surgeon, plastic surgeon or dermatologist should be able to help you.