Mass Redistribution in a Finite Universe: The Full MRET Theory Description:This preprint presents the complete formulation of the Mass Redistribution Expansion Theory (MRET) — a novel cosmological model in which the apparent expansion of the universe emerges not from dark energy, but from the geometric response of spacetime to the redistribution of mass into collapsed structures such as black holes and superclusters. MRET assumes a finite universe in both mass and volume. In this framework, a dynamic scalar field φ evolves in response to large-scale structure formation, stretching spacetime and producing the observed acceleration of the cosmos. The model requires no cosmological constant, no exotic particles, and no infinite boundary conditions. This compendium includes: The foundational motivations behind MRET Six governing rules of the theory Step-by-step derivation of the scalar field equations and α(z) redistribution strength A full set of predictions for key observables: H(z), φ(z), ρ_φ(z), fσ₈(z), κ(r), and CMB power spectra Comparisons to data from DESI, Planck, SDSS, and Pantheon+ Detailed appendices including equations, parameters, simulation notes, and residual diagnostics