Shared-aperture technology for multifunctional planar systems, performing several simultaneous tasks, was first introduced in the field of radar antennas. Recently, the shared-aperture concept has been suggested as a platform for multifunctional optical phased array antenna, accomplished by a reflective metasurface. Metasurfaces consist of metallic or dielectric subwavelength nanoantennas, capable of manipulating light by controlling the local amplitude and phase of an incident electromagnetic wave. Effective control of the electromagnetic response of the metasurface can be acquired by the geometric phase mechanism, also known as Pancharatnam-Berry phase, which enables spin-controlled phase modulation, where the photon's spin is associated with the intrinsic angular momentum of light. Here, we present multifunctional spin-dependent dielectric devices, based on shared-aperture geometric phase metasurface (GPM), and demonstrate multiple-beam technology for optical sensing and characterization. The shared-aperture GPM was realized via the interleaving of sparse antenna sub-arrays, thus resulting in a Si-based metasurface consisting of multiplexed geometric phase profiles, and generating multifarious beams, e.g. wavefronts carrying orbital angular momentum. The obtained on-chip nano-device was employed as an optical rotation sensor and a spectropolarimeter, integrated with an angular momentum detector which facilitates complete real-time control and measurement of the frequency, polarization, phase, and orbital angular momentum of light.