Elevator pause: All you have to do is hit the pause button and the interact button at the same time, in my case. I press "Q" and "E" while looking at the monitor. You should be able to input all 10 numbers at once, click check, and then tap return to get out of pause screen.
Watermelon glitch: Tested it, place watermelon piece out of Marzia's pathway and be within range of that piece. Marzia will run up to you and just stand there, if done successfully.
Screenshot: Marzia standing next to me inside the elevator.
Also, biggest tip. Marzia can't open doors at all before the final chase in current version! Lure her into one of the 6 beginning classrooms, and pray she doesn't get released by Headteacher. Makes beginning part easier.
(Let me know how it works out.)