Walk through walls
On levels that allow you to travel upwards or downwards greatly as you progress as Sonic, go to an area where Knuckles' path starts. Hold down and wait for the screen to drop, then jump (do not spindash). If done correctly at a area that will cause this, the screen will shift and scroll in a loop back to you. During this time, you are free to walk through walls. This can also be done in select areas of levels where there is no path for Knuckles.