Holding up before and during the spinning green platforms causes the next one to spawn faster, saving time.
At the end of the level, a gatehack using a forward spit enemy can be done to open the gate to the exit pipe. In order for it to work, you must tongue one of the green spikey guys or its pot, give it a negative (left) x speed, such as by spitting it against the gate and having it bounce backwards, then respitting it into the gate. This is shown in the gif below.
However this gatehack requires the gate to be spawned with a correct camera position. An easy method to do this is to run down the last couple of edges rather than jumping down them.