New super mario bros DS world 7

Hello, to unlock the last green mushroom house, you need to play in world 7-4:
First, you need a mini mushroom (you can find one in world 1-4)

After starting, jump on the blue and white things that propel you into the air and try to land on the pink mushrooms.
Or if you've reached the checkpoint (the flag with the red mushroom), continue upwards. Jump on the thing that propels you into the air next to it and go to the pink mushroom on the left, then thanks to the pink mushroom, jump on the flying question mark block. There will be a small hole, enter it and try to jump towards where the mini pipe is, then enter this pipe and go to the flag.
And there you go, it's done

Don't forget that you must keep your mini mushroom until you enter the mini pipe.

If you didn't understand, let me know and I'll explain it to you again.

You need to create a new world around you and it will give you a fireworks display and special music (I'm almost sure ...)
But I'm also stuck...