# Is twisting a corner of a Rubik's cube a valid move?

I believe the question is self-explanatory but I'm asking the question in different contexts. I understand that it makes the 3x3x3 unsolvable if you twist a single corner but there are cases where it could still be solvable if you twist pairs of corners, although I'm not sure of the mathematics behind twisting a corner of a Rubik's cube. Here are the contexts which I am particularly interested in

• Is it a valid move in the intended original cube? Is the move "allowed" as it seems to be only available in modern constructions of the cubes

• Is it a valid move in speedcubing? I have faced some special cases where twisting two corners would dramatically speed up solving a 2x2x2 layer

• Do you mean twisting one corner completely by itself? (As in not rotating edges to twist the corner, but just grabbing the corner and basically snapping it into an incorrect alignment.) If that's what you mean, then no, it's not a valid move. – dcfyj Aug 11 '17 at 14:24
• Yes, exactly "grabbing the corner and basically snapping it into an incorrect alignment" – Syafiq Kamarul Azman Aug 11 '17 at 15:21