I was wondering how to complete this challenge, and I saw from ChrisHateZ answer to a similar question that you need to:
"...transport this postcard over your whole journey in the cave to return it right at the end.
Since this method is obviously tedious, I'm wondering if it would not also be possible to:
Leave the postcard on the ground somewhere in the lobby, then return it to the rack right at the end of the game.
Does my proposed alternative method work? Essentially the question boils down to whether the achievement is tied to the final object interaction, or whether it is tied to a process of steps that have to be taken in a specific order. I'm also interested if the steps for the "Shoplifting" achievement must be completed on the same run as the "Remorse" achievement.
Given the very long period of time it takes to get this achievement, it would be very helpful to me if someone could confirm the exact requirements before I attempt it.