Masks used in our analysis to mimic CMB-S4 sky coverage, shown in Ecliptic coordinates with Galactic emission at 145 GHz in the background. (a) The left panel shows the mask used for component separation for the wide sky survey corresponding to the LAT configuration (f_sky = 0.64). (b) The middle panel shows the mask used for lensing reconstruction for the wide sky survey (f_sky = 0.37). (c) The right panel shows the sky area considered for the deep survey corresponding to the SAT configuration, which was used for the delensing study (f_sky = 0.025).