Current widely accepted understanding of the origin of motion is based on the presumption of an external force or agency required to impart motion to a classical mass. Part I of this paper [A. Singh, Physics Essays, 31 , 467 (2018)] describes the missing physics of the origin of motion based on the well-established principle of mass-energy equivalence which requires a nonzero rest mass for originating spontaneous nonzero kinetic energy or motion. The proposed Universal Relativity Model (URM) based on special relativity theory describes a universal model predicting classical as well as quantum behaviors of both massive and massless particles in a single model that is shown to remove prevailing deficiencies/inconsistencies and paradoxes of the current widely accepted physics and cosmology... theories. The proposed model describes a spontaneous (no external force or agency required) relativistic mass creation/dilation process observed during wave-particle behavior allowing a nonzero photon mass at rest (emission and absorption), which dilates to zero as it expands and accelerates to the speed of light through uninterrupted space. The model thus bridges gaps between relativity and Maxwell’s theories. This (Part II) paper extends the URM model to describe the physics of the observed spontaneous complementary or dualistic wave-particle behavior of quantum particles as an alternative to the existing de Broglie model. The proposed models explain as well as provide mathematical formulations of the observed transition from classic to quantum behavior including the effects of gravity at quantum scales. The models also provide a physical understanding and resolution of well-known and as yet unresolved paradoxes related to the measurement problem or the observer paradox (collapse of the wave-function), spooky action-at-a-distance or nonlocality, Heisenberg’s uncertainty, and parallel universes. Finally, URM provides a new perspective on physical reality entailing a complementary set of relativistic realities (subuniverses) within a single universe.