Hello!
We ask you to please thoroughly read the VEX Skyrise Game Manual and to please review the Q&A Usage Guidelines before posting in this forum. Specifically, please quote the rule or definition that your question is referring to.
The restrictions on modifying Robots are explained in both <R1> and <R2a>. I’ve quoted both below for your convenience.
<R1> Only one (1) robot will be allowed to compete per team in the VEX Robotics Competition. Though it is expected that teams will make changes to their robot at the competition, a team is limited to only one (1) robot. The VEX Robotics Design System is intended to be a mobile robotics design platform. As such, a VEX robot, for the purposes of the VRC, has the following subsystems:
Subsystem 1: Mobile robotic base including wheels, tracks, legs, or any other mechanism that allows the robot to navigate the majority of the flat playing field surface. For a stationary robot, the robotic base without wheels would be considered Subsystem 1.
Given the above definitions, a minimum robot for use in any VRC event (including skills challenges) must consist of 1 and 2 above. Thus if you are swapping out an entire subsystem of either item 1 or 2, you have now created a second robot and are no longer legal.
<R2> Every robot will be required to pass a full inspection before being cleared to compete. This inspection will ensure that all robot rules and regulations are met. Initial inspections will take place during team registration/practice time.