Gained and lost weight, double chin - What procedure wild help with my neck? (Photos)

Chin Liposuction and Thermitight
Chin liposuction helps reduce the bulge under the chin and can be done for the whole neck. Once the fat is removed the skin can become loose and saggy in some cases. It can be avoided by combining it with Thermitight which is a radiofrequency heat delivered under the skin to tighten it. Both chin liposuction and Thermitight can be done at the same time. The recovery is fast and it can be done under local anesthesia.
Click on the video link below
Regards
Dr. J

From the photos that you have provided it appears that you are dealing with normal aging of the neck. There may be some isolated fat but the bigger issues are the laxity of the skin and platysma muscle. Fillers and Botox have no role at all in this area. You will need a facelift surgery that addresses the platysma muscle and perhaps the fat and muscle beneath these muscles in the neck.