Thanks for your feedback.
Normally you see an information that is the end of the build, but is it possible that it is missing at some place. Sorry for that.
And Sina and Karen have say goodbye in the story to the player. But Karen comes back for a small visit if you are on her route. Sina and Karen are not in the SC, only Karen's event is currently inside the SC.
Random events have nothing to do with the unique events. It's not possible to miss a unique event, except you are on an other road of course.
The SC is Beta and will be improved and then it is finishes it will of course have inside all certain situations. That's then the walkthrough.