Your chin is too small and if you have class II bite, you would need two-jaw surgery.If your bite is normal, you could have genioplasty.12mm is too many to advance just one osteotomy and two step genioplasty is better for you.
This degree of chin protrusion is a combination of excess bone AND soft tissue. Your chin reduction should be from a submental approach where the both the excess bone and soft tissue can be removed. Any intraoral chin reduction approach will not deal with the excess soft tissue chin pad which...
You can not move the bones of your face forward unless you are willing to adversely affect your bite. Thus a flat midface and infraorbital rims need to be augmented. Bone augmentation using custom designed implants would be the simplest and most effective method to bring the midface forward....