Hey sorry for the late reply!!
To get ending 4, you need to have 0 or less affection points by the time you finish the rollercoaster section (so pick all the negative choices you can up to that point), and pick “Don’t do anything” when Liev is about to attack the bullies. (I just realised that I forgot to include this important step in the guide…)
** MASSIVE SPOILER!! **
He will murder the bullies, at which point you need to choose “Make a run for it” to get Ending 4!!
To get ending 6, see the endings walkthrough: https://lucia-lily.itch.io/pulsatio-cordis/devlog/849428/ending-and-cg-guide-a-new-build
Hope this helps!