A bush you can push, hehe, that's a classic.

I'll keep that one in mind, That's obviously a flag left on a screen when I removed a certain warp there. Thanks for the notice.

Level 4 is located in the forest world, but the only way to get to that area is by taking a warp in the flooded world, that warp is in a cave very near the cave from which you first entered the flooded world from the ice world. On that same Island to be exact. =p You'll know you're on the right track when you find Relenia Castle.

A better sword will be available to you once you obtain the hookshot and an upgraded bracelet. You'll find the new sword when you adventure the Temple of Time in the ice world. It will warp you to the sword and that very warp is a very nice shortcut to level 5.