A solid body retains its own shape for a long time. Does it necessarily have a crystalline structure?

most often the body retains its shape for a long time and has a crystalline structure, but if the temperature is low, then even with a random arrangement of molecules, the body can retain its shape.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.