Because B12 in its organic form comes from animal sources like fish, meat, eggs and dairy, vegans, vegetarians and people with nutrient deficient diets need B12 supplementation to meet minimal health requirements
It targets melanocortin receptors to influence processes like skin pigmentation and appetite control
Some of them, yes, and the evidence is strong
Yes, it can often be taken with other supplements or medications
Kade IJ, Balogun BD, Rocha JB
The peptides relatively short half-life in the bloodstream does not affect its stability in storage, but certain conditions can degrade it quickly