Since launched, Fermi has been extensively monitoring the blazar gamma-ray emission. Thanks to its timely flare alerts, a large amount of high-quality simultaneous multi-wavelength data have been collected. These multi-wavelength spectra, light curves, and polarization signatures contain crucial information about the jet physics in the blazar zone. We have performed first-principle plasma and particle simulations coupled with polarized radiation transfer to bridge the gap between theories and observations. Our approach self-consistently treat the magnetic field evolution and particle evolution that are essential to the blazar emission, and calculate time-dependent multi-wavelength radiation and polarization signatures that can be directly compared to observations. In this talk, I will present two great opportunities that Fermi flares and optical polarization signatures can help us to understand the underlying particle acceleration mechanisms during blazar flares, namely, distinguishing kinetic- and magnetic-driven flares, and identifying magnetic reconnection events. Finally, I will demonstrate the potential of high-energy polarimetry on understanding blazar radiation and particle acceleration mechanisms and its feasibility.