Hi I m kanika.. I was fair. But now because of suntan my skin(full body) has became black. Can I use

You cannot remove a suntan without removing the skin that contains the tan. A suntan is caused by the increased production of melanin in individual cell to darken it in order to protect itself from UV rays.
Chemical peels can be used to remove layers of skin that contain the darkened cells but most are illegal and the legal ones have very harmful side effects including chemical burns, increased risk of cancer and cell poisoning. It is NOT recommended that anyone use them.