Short answers, pulled from the story.
Albert Einstein completed a fifty-page account of his theories in March 1916. He published the German version titled Über die spezielle und die allgemeine Relativitätstheorie, gemeinverständlich later that same year.
Results from an eclipse expedition caused a major stir in December 1916 after Arthur Eddington confirmed light should curve towards a massive body during his 1919 eclipse expedition. These results provided strong evidence for the validity of general relativity by matching observations with strict accuracy across different astronomical phenomena.
Einstein used the observation that a piece of lead and a piece of wood fall in exactly the same manner in a gravitational field when starting from rest to argue that gravitational mass equals inertial mass for all bodies. He asked readers to imagine an occupant inside a chest accelerating freely through empty space who would conclude they were at rest in a gravitational field because released objects approach the floor with accelerated relative motion.
Alexander Friedmann showed in 1922 that the theory demands an expansion of space. Hubble later investigated extra-galactic nebulae known as milky ways where spectral lines emitted by these nebulae showed a red shift increasing regularly with distance, confirming what Friedman had derived from the field equations of gravitation.
The theory predicts the correct value of 43 arc-seconds per century for Mercury's orbital precession. Newton's theory could not account for the precession of Mercury's perihelion but general relativity predicts the correct value strictly in agreement with observation.