I found two glitches throughout a playthrough of GT. Number 1 is hard to get, but it was probably likely from the beginning. Anyways, here they are.
1. Heal after beating level, but get stuck. The screen flashed, and I couldn't move GT at all. Wrong moment to heal, I guess.
2. After getting all 55 Orbs, I did the tutorial again, but after saving the "Green Robot" said congrats for getting all the orbs. Both GT and the other robot stayed frozen, but another GT which I could move was there.
But, if I didn't move GT, and instead boosted I got outside the bounds.
See?
This showed me a tutorial orb, that when touched took you straight to the tutorial.
And I could even face bosses outside ..