Answered: Stack Prevention

Please view the attached pictures to better understand my questions. They correspond by number to the questions.

#1) If there is no cone legally stacked on the opposing alliances stationary goal, or there is an illegally stacked cone on it, can you place a c channel against either the goal or the illegally stacked cone so as to prevent legal stacking?

#2) If a cone is already legally stacked on the opposing alliances stationary goal, can you place a c channel against the legally stacked cone so as to prevent the further legal stacking of more cones?

#3) If the opposing alliances stationary goal has 1 legally stacked cones on it, and this legally stacked cone has an illegally stacked cone on top of it, can you place a c channel against the illegally stacked cone so as to prevent the further stacking of cones?

#4) Do these rulings also apply to the same scenarios, except with mobile goals? If this is to much of a blanket ruling since mobile goals can be in so many situations, lets say they are sitting outside of any scoring zone and are not being controlled by an opposing robot.

#5) If these are illegal, does the legality change if the c channel is not touching the goal, however it is very close and serves the exact same purpose as it would if it were touching it?

I would think that all of these scenarios are legal. #2 specifically I think would be legal due to the definition of stacked:
“A Cone is Stacked on a Goal if it is not touching a Robot of the same color Alliance as the Goal and either:
a) FullynestedonaGoal(seeFigures5&6).
b) FullynestedonaStackedCone(seeFigures7&8).”
Since a blue robot is touching a cone scored by a red robot the cone is still stacked, so you are not breaking no unstacking rule.

Please note that in none of these scenarios is the robot pushing the c channel under a cone that is already stacked, it is simply preventing the further legal stacking of cones.

This technique can be seen on video here at 3:07: Vex In The Zone - 8059 SingVEX Reveal 2017 - YouTube

Here is the what the different colored cones in the images mean:
Yellow: Cone legally stacked before c channel is put in position.
Red: Cone illegally stacked before c channel is put in position.
Green: Illegally stacked cone that is placed after the c channel is put in position.
#1-01.png
#2-02.png
#3-03.png

First - there is no such thing as an “illegally Stacked Cone”. We assume, based off of your pictures (thanks, by the way), that you are referring to a Cone that is not fully nested, and therefore not considered Stacked.

Provided that <SG5> is not violated and no Stacked Cones become un-Stacked, there are no rules preventing this type of maneuver. Please see this similar Q&A: