Clause B of rule <R4> and clause A of rule <SG1> both specify (bold added here for emphasis) that at the start of each Match, the Robot must fit within the volume of a Starting Zone, which is defined as:
Starting Zone – One of two areas of the Field where Robots may begin the Match. Starting Zones are infinitely tall 3-dimensional volumes, bound by the inside of the Field Perimeter walls and the inside edges of the black lines marked by yellow VEX IQ beams. See Figure SZ-1.
To answer your three questions directly:
- The Robot cannot overhang the wall in its starting position.
- No part of the Robot, even a motor, can expand over or beyond the field perimeter at the start of a Match.
- Yes, the inside edge of the field perimeter corresponds to an infinitely tall plane that cannot be crossed by a Robot in its pre-Match setup.