Ahhhhh thank you so much for the in-depth review! I don't mind it at all! I'm so appreciative of the fact you took the time to go in-depth and comment on several aspects of the demo! And I'm glad to see it was an overall positive experience for you! I can't say that my comment will be nearly as long as yours. However, I'll try to address some of the things that you've mentioned!
Yes, pressing F or F11 toggles fullscreen mode. :) I've made this (hopefully) a little clearer on the controls screen for the full VN build. In regards to the self-voicing, I was able to decrease the font size of the message. And I managed to find a way to silence the notifications for the screenshots. However, I'll be leaving the feature of self-voicing speaking the menu options, as the self-voicing feature was originally intended to make navigating the menus more blind-friendly. Your suggestion for those that don't need SV during the menus is a good suggestion as a workaround. :)
I'm really happy that you were getting the Undertale feeling in some aspects! And I'm happy that it's giving you a feel for what the full game will be like! I'll choose not to comment on the things you've mentioned regarding the story. All I have to say is, you'll see when it all unfolds. ;) I'm truly excited to see what you think! Thank you again for your comments/review! :D