Level 8 - Star Road 1
Simply head all the way to the far right of the screen and then do a spin jump. Mario will tunnel his way down to the key and keyhole.
Level 9 - Star Road 2
Get the blue baby Yoshi and eat the star to make him full-size. Avoid the fish until you reach the green pipe. Swim under the pipe to reach the keyhole.
Level 10 - Star Road 3
Knock Lakitu out of his cloud, then hop in and float up through the hole at the top of the screen. Get the key from the left and take it to the keyhole on the right.
Level 11 - Star Road 4
Hold a non-red shell in your blue Yoshi's mouth. This way he can fly and, by holding down while spitting the shell, drop it on any solid platform in front of him before he swallows it. Keep doing this and you've got limitless flight power. Flutter under the pipes to reach the secret exit.
