Found a walkthrough and it says for the forest...
"Each area in Forever Forest has four exits, but only one will advance you in most cases. To figure out which exit to take, look for slight differences in scenery near the correct exit. In the first area, the exit is on the opposite side of the entrance. Look at the flowers to be sure.
In the second area, the exit is one to the left of the entrance. You can see eyes appear on this stump in the background.
In the third area, again, the exit is one to the left of the entrance. This one has four flowers instead of three.
The next area has a Bub-ulb in the middle of it. Hunt around for it.
The exit to the area with the Bub-ulb is one to the right of the entrance, and is the one where the scary face appears on the tree.
Now we'll take a little detour. Go through the exit that is one to the right of the entrance. In this area, there is an HP Plus Badge. Get it and get back on the main path (take the exit with the beehive near it).
Now that you're back on the right path, the correct exit is one to the left of the entrance. There are more mushrooms near this exit than the others.
The next area's exit is one to the right of the entrance. The flowers here stay when selected, while the other flowers disappear.
Time for another quick detour. Head to the exit that is on the opposite side of the entrance here. In this area, there is an FP Plus Badge. To get back on the main path, take the exit near the flowers you can select.
You can reach the exit from here. Simply take the exit near the sign."
Forest level link
Full walkthrough here
Hope this helps