Shevuot 7 - May 8, 10 Iyar

From where is it derived that the verses that obligate one to bring a sliding scale sin offering if one is impure refer to one who entered the Temple or ate sacrificial items? Four different answers are brought and analyzed. Some are rejected. From where is it derived that the sin offering of Yom Kippur offered inside is to atone for one who entered the Temple impure or ate sacrificial items when they knew at first they were impure, then forgot and then didn't remember?