What are the 3 principles of heredity that Gregor Mendel discovered?

Based on the information shared by the experiments of Gregor Mendel, the statement "traits are passed from parents to offspring independently of one another" is actually a theory and not a hypothesis or observation. It cannot be a hypothesis as it is already tested and proved. Hypothesis is something that has not been proved. An observation is something that has been observed, but never proved. Gregor Mendes proved this theory or hypothesis in the laboratory and so it is surely a theory.