Is it possible to get all the scenes and still get the true end? How much submission and events are allowed by the end of the game?
Theoretically, as long as you meet all of the right conditions, you can reach the True Ending at any point as long as Kana doesn't hit 1200 submission.
In practice though, considering the random nature of events, plus the fact that some stuff doesn't happen without Submission hitting 800 and that said milestone also adds an event that cannot be interrupted during the night phase at times which tends to add a lot of submission...
Quite frankly, it's probably impossible on a 1st playthrough. The more intense the events, the more submission they add... and if I remember right, the day-time anal events need 900 submission to trigger with any regularity.
On top of all that, there's some scenes that only trigger at lower submission values, a couple of the porn videos made by L. The exhibitionist stuff requires body development and body development partly depends on submission... Then there's the two "L is angry" scenes that have low and high submission variants. Or the one scene when Kana and MC are still living separately...
There's also the fact that the True Ending can only be done by beating the final boss, which can only be accessed while L is away. Which means that it's really hard to manage the submission values.
Maybe it's possible with really extensive save scumming? I honestly don't know. I don't think anyone's tried this.