how do we get to other scene or unlock certain things to decide for the ending
Many.I lost count of them.As I said,at the start of shift 2, deciding between ignoring or replying to Lance and bringing the umbrella with you or not can lead to different routes. Also,choosing smth out of the menu when you drink w Amelia also opens >2 endings. Haven't found all endings yet but there are ones where BB rides you home.
Our mother-in-law spent a lot of time writing this masterpiece, so it will take quite a long time to figure out different endings.
I try my best not to spoil you, so my hints are vague. If you need help, feel free to ask me.