It's generally not recommended to give away a 20-day-old Japanese Spitz puppy. At this very young age, the puppies are still completely dependent on their mother's milk and haven't yet been weaned. Their immune systems are also quite fragile, making them highly susceptible to illnesses. Separating them from their mother and littermates at this stage can be incredibly stressful and detrimental to their health. Therefore, it's best to wait until the puppy is around six weeks old (or a month and a half), when they are more independent and their bodies are stronger.
A 20-day-old Japanese Spitz is simply too vulnerable to be rehomed. They are still in the process of transitioning away from their mother's milk and are usually not yet eating solid food or puppy kibble. The stress of a sudden change in environment can easily trigger stress and other reactions and increase their risk of contracting diseases due to their still-developing immune systems. It's strongly advised to wait until the puppy is approximately six weeks old before giving them away. By then, they should be eating puppy kibble, which provides the necessary nutrients for their growth. When you do decide to rehome the puppy, prepare puppy supplies for the new owner beforehand including their usual puppy food, feeding bowls, some familiar toys, and a blanket that smells like their mother and littermates. The familiar scent will help them feel more secure and adapt more easily to their new home. It's also crucial to have an open line of communication with the new owner. Provide them with detailed information about the puppy's care, feeding habits, and any health considerations. This will significantly increase the puppy's chances of smoothly settling into their new home.