which is the size of the robot?
None of the above… it is X and Y (length and width) should be 11" and Z (height) should be 12"… but remember if it is 12" on Z it may be possible for it not to be able to pass under the hanging bar and on X,Y it may be bigger than the specified 11" as long as the part actually touching the field is 11" or less.
The starting constraints are explained in <R3> of the VEX IQ Challenge Game Manual: