Internal profiles of a 12 M_⊙ single-star model from Set I accreting at 1.0 × 10⁻³ M_⊙ yr⁻¹, shown as a function of radius coordinate. Colored lines correspond to six snapshots covering the phases before mass transfer, during mass transfer, during thermal relaxation, and after restoring TE. The reference time t₀ = 10.06 Myr. Panels: (a) enclosed mass; (b) density; (c) luminosity; (d) gravitational energy generation rate (positive=contraction, negative=expansion); (e) opacity; (f) entropy; The thin vertical dashed-dotted lines in Panels (d), (e) and (f) mark the radius of the iron opacity bump. (g) angular velocity; (h) enclosed angular momentum; (i) log I (solid lines) and log(J/ω_surf) (horizontal dotted lines), where J, and ω_surf denoting the total angular momentum, and surface angular velocity at the corresponding snapshots. The relation I = J/ω_surf corresponds to rigid rotation, while I > J/ω_surf indicates differential rotation, with the core rotating more slowly than the envelope.