This place is crawling with Bob-ombs, especially because there are blocks that keep spewing out more. Some item blocks are arranged in pyramids. Use the Bob-ombs to hit all of the blocks in the pyramid at once. Once of them has a Super Leaf, giving you the Tanooki Suit. Go past the Piranha Plants and you'll see a POW Block on the wall. Use it to reach the first Green Star. Ahead is another POW Block. Follow the chain to the end to get the 1-up. You can reach it near the midpoint.
Ahead is a bunny on a circular platform. Chase it down on the inside part of the circle to catch it for the second Green Star. Ahead are a couple of Goomba stacks in front of a crack in the wall. Use a Bob-omb to break the wall. Go behind the wall for the stamp. Go back in front of the wall and take a pipe to a cloud. The cloud cannon launches you to an area in the sky with tiles. Clear the tiles with the help of the Bob-ombs, revealing 8-bit Mario and the third Green Star. Drop back down and use a Bob-omb to start a chain reaction with a POW Block. Run ahead as the POW Blocks clear out the Piranha Plants for a 1-up. Go through the pipe. Use a Bob-omb to make stairs to the flagpole.
The stamp is of a Bob-omb.
Completing the level will give you access to a Sprixie House. The stamp is of the orange Sprixie Princess.