Age 28. What are my options for loss of volume, sagging, marionettes and a sad mouth? (Photo)

Thank you for your question and pictures.  You do not have loose skin for surgery, therefore nonsurgical options such as injectables like filler to soften your marionette lines.  You could try and achieve an upturn for your lip by using lip filler, or a lip lift would be the best permanent solution.  Please make sure you find a reputable and qualified plastic surgeon who can assess you properly to give you a realistic idea of what outcome you can achieve.  All The Best 

Sagging and volume loss of the face at early years (eg 20s) is usually related to weak cheek bones.Cheek bones are the foundation of a youthful ("lifted") facial appearance. When the cheek bones are weak, the midface tends to sag, corners or the mouth tend to go south and marionette lines starts to form. Augmenting the cheek bones could reverse the signs of aging. Cheek bones can be easily augmented in the office setting with soft tissue fillers like voluma or surgically with implants (medpore implants)

Thank. you for your question and photos. Most of the time, reversible noninvasive treatments are best for early aging in our twenties.  Healthy nutrition and good skincare followed by non invasive skin tightening procedures like Ultherapy and radio frequency micro-needling could be considered.  Your skin should respond well to these modalities by tightening and  producing collagen. Further lifting and supporting of tissues can be accomplished with a conservative combination of Botox and HA Fillers. An in person evaluation to assess the extent of true skin laxity is also recommended. 
Best,
Dr. Stephen Fink