I can't start episode N or O; investigating every inch of the Orthrus building from the outside as Tristadecca does absolutely nothing (including the window with a green arrow pointing to it, as she just says she won't break it), and there's nothing to do in the Freedom Real Estate Office either (I've also got Lasca 4).
Do these episodes need me to start at a specific episode number? For reference, I'm currently in episode 11, and I can't start either of these in episode 10 too. I've also done both of the bad endings that result from episode 11 (I'm assuming they're episode 12a and 12b).
Also, my gut says that all stamps are eventually obtainable regardless of what paths you took earlier; is this true?