Do bio collagen buttocks injections actually exist? Is this illegal?

No injectables/fillers are FDA approved for buttock enhancement or augmentation. This is because they all have potential dire consequences either immediately (i.e. pulmonary embolism and death) or in the long term (eg. high risk of infection, extensive scar tissue formation and hardening, skin discoloration, migration of the product down into the legs and/or vulva, and extrusion through the skin). Even the “plasma” injections are a gimmick that simply will not work. Fat transfer is an option, however, buttock implants are the only relatively safe and permanent option. Glad to help. 

The information you provide is a bit vague,but generally I recommend to be very cautious with these things.Especially in the butt augmentation  sector there is a whole shadow industry claiming to have easy and quick solutions not requiring surgery.I have never seen anybody coming out of this with any decent result, but I have seen many people with disastrous consequences requiring reconstructive surgery. If you are determined to have something injected make sure that whatever it is it should be absorbable.

I do not recommend having injections of products that are not FDA approved into the buttocks. I see many patients that have had free silicone injected into the buttocks and various areas of the body.  Patients suffer with chronic pain and deformity when non accredited providers inject foreign body unregulated substances.  There are many ways to help patients who suffer from silicone injections.  Liposuction is a great option.  I recommend seeing a plastic surgeon to provide an evaluation.