I think each warp gate automatically warps you to a certain level IF you reached it. For example, the warp gate in level 1 kept warping me to level 6 (? I don't remember lol) before I finished to level 20.
If you have extra wiimotes laying around you can "cheat". Press the A button to make a cursor appear on the tv and while yoshi is moving (i.e. after you've drawn the line and hit go) each remote can remove one fruit from the board per level. This does NOT fill up the bar at the bottom though, so you can't get eggs out of it and I think if you use it too much and the bar empties you lose.