Next to this golden chest, there is a yellow button. Push it and go to the center of the area with the two pipe entrances. Take the pipe that leads to the bigger fenced area. There, push the red button. The red block disappears and you can use another pipe to get to the chest.
Continue the story path, up a wooden bridge path, across a battle area. Right before this battle area, there is a cannon to the right. But you can't use it yet. But... There is another wooden bridge. Go across but don't go to the next battle area yet. To the left, there is a tunnel. Use it to get to the other side and push the red button. This unlocked the cannon. Use it to get to the chest.
In the Challenge 2 Battle area, before you meet the sunflower in the story, there is an area to the right with a lot of coins. There you can move away a block to get to the chest. Note: Get the MOVE! ability at the End of World 1
Take the cannon next to the chest you just opened. You'll get to the next chest. Here, you can also push the rabbid button to get access to the normal walkways. But I take the cannon back to where I came from...
Continue to follow the story path until you get to the empty battle area before Challenge 3. Instead of going right, down to challenge 3, go straigt ahead. You should see the coin. Walk around the mountain to get to the chest.