In this talk, I will present the methodology behind the new code, 'requiem2d', a Bayesian framework that combines HST 2D grism spectroscopy with HST and Spitzer photometric data to constrain the spatially resolved stellar populations and measure age and star-formation rate gradients. This code is developed for the purpose of analyzing the REQUIEM^2D Galaxy Survey, a sample of 8 strongly lensed quiescent galaxies spanning redshifts of z = 1.6 − 2.9 and stellar masses of log M* = 10.4 − 11.5. I will present tests using massive mock galaxies selected from the Illustris cosmological simulation. Furthermore, I will introduce results from our REQUIEM-2D pilot target, MRG-S0851, a gravitationally lensed quintuply imaged massive compact red galaxy at z=1.9 with a significant recent star-formation activity. Using our recovered ages and SFHs from the requiem 2d joint spectro-photometric analysis, along with trajectories in the UVJ and NUVrK color-color diagrams, we find that MRG-S0851 is consistent with an early forming, slow quenched galaxy that is going through a centrally-concentrated rejuvenation phase.