First Man (2018)
As for the Agena (designated "GATV-5003"), it was in good shape and NASA was able to control it from the ground. During the Gemini X mission, Armstrong's future Apollo II crewmate Michael Collins retrieved the Agena's meteorite collection tray. NASA continued performing many test procedures and maneuvers with the Agena until its fuel and batteries eventually ran out.
As for the hatch, due to the malfunctioning explosive hatch bolts in Gus Grissom's Mercury flight, the hatch for the Apollo I was designed to maintain pressure. In order to open it, Ed White had to reach a lever above his head and pump it several times, after which the hatch would pull inwards and then swing out, somewhat like the doors of an airliner. If not for the Mercury malfunction, the Apollo I hatch would have had explosive bolts, in which case it is possible that at least one of the crew might have survived. An embarrassing discovery in the aftermath was that of a wrench that had been misplaced during capsule assembly and was found behind a sealed panel. While the wrench had nothing to do with the fire, it indicated a degree of carelessness in the assembly of the spacecraft.