The growing demand for high-capacity communications and multifunctional electromagnetic systems requires components capable of independently manipulating multiple frequency bands and polarization states within a shared aperture. This work addresses the challenge of achieving fully decoupled, multi-channel wavefront control on a single metasurface platform. We propose and experimentally demonstrate a reflective metasurface with a composite “nested” resonator architecture for quad-polarization, dual-band operation. The meta-atom comprises an outer double-split ring resonator and an inner cross-shaped orthogonal ellipticalpatch. These two substructures excite independent resonances at 6 GHz and 14.5 GHz, respectively, with electric-field distributions confirming physical isolation between the two frequency bands. At 6 GHz, the outer ring dominates, where geometric and propagation phase mechanisms are synergistically combined to achieve complete spin-decoupled control of left-hand circularly polarized (LCP) and right-hand circularly polarized (RCP) waves, enabling independent 2-bit phase encoding for each spin channel. At 14.5 GHz, the inner patch governs the response, utilizing the propagation phase principle to deliver independent 2-bit phase modulation for X-linear polarization (XLP) and Y-linear polarization (YLP) waves with high polarization isolation. Full-wave analysis confirms physical decoupling of the resonant modes, establishing four non-interfering manipulation channels. A 21×21 array prototype was fabricated and tested to simultaneously generate four distinct vortex beams, each carrying a unique orbital angular momentum (OAM) mode (topological charges of +1, +2, +3, and +4) and directed to a different predefined angle. Far-field measurements in an anechoic chamber show excellent agreement with simulations. The generated beams exhibit the characteristic “doughnut” amplitude profile and well-defined helical phase fronts, with measured beam-pointing angles precisely matching theoretical predictions. The measured mode purities reach 0.74, 0.72, 0.78, and 0.75 for the four channels, respectively. The measured beam-null angles are -15° and +15° at 14.5 GHz, and -18° and +18° at 6 GHz, matching the theoretical designs. Inter-channel crosstalk is verified to be extremely low. This study provides a compact methodology for fully independent, multi-polarization, multiband wavefront engineering. The demonstrated capability to generate multiple high-quality OAM beams from a single shared-aperture device represents a significant advancement for mode-division multiplexing communications, multi-channel radar, and integrated electromagnetic systems.