The shot itself takes seconds, plus a couple of minutes of intake
It does not, as long as you maintain gentle technique throughout
A doping/sport note (because it comes up in searches) WADAs prohibited list explicitly references growth hormone fragments, including AOD-9604 / hGH 176191

Patients who have undergone gastric banding should be aware of the following signs that may indicate falling B12 levels and warrant prompt blood testing: Neurological symptoms: Tingling, numbness, or 'pins and needles' in the hands or feet Difficulty with balance or coordination Memory problems, difficulty concentrating, or 'brain fog' Mood changes, including low mood or irritability Haematological symptoms: Persistent fatigue or weakness disproportionate to activity levels Breathlessness on mild exertion Pallor or a slightly yellowish tinge to the skin Other indicators: A sore, smooth, or inflamed tongue (glossitis) Mouth ulcers occurring frequently It is important to recognise that some of these symptoms particularly fatigue and low mood are non-specific and may overlap with other post-operative nutritional deficiencies, such as iron or vitamin D deficiency
Every 1 mg of dose is 0.2 mL, which is 20 units at this concentration
Individual responses vary, but some individuals may experience improvements in energy levels and symptoms within a few days after starting B12 injections.