How to get to level 4 and 7 on Nintendo DS New Super Mario Brothers game

Hi does this happen with any other games an super mario brothers has certain save points

You can get the walk through on link below.

http://guides.ign.com/guides/682879/page_3.html

Go here - http://uk.guides.ign.com/guides/682879/page_22.html

super mario ds. on world 4 level 5, how do you get the third coin

Use a mini mushroom

In World 7 - 4 (I think its World 7 - 6), use MINI Mario or Mini Luigi and hit bombs and throw bombs to make them explode and go to the tiny hole and ull end up somewhere  and ull beat the level and ull get to past the land to get to World 7 - 7

you need to beat the castle in level six while being mini- mario and it will open up level 7.

You Can Only Save Once You Have Passed A tower Or Castle! You Can Also Save If You Open A Mushroom!

WHAT SECRET LEVELS DO YOU MEAN WORLD 4 AND 7
I KNOW THE SOLUTION JUST GO ON WORLD 2 THEN GET A TINY MUSHROOM THEN FIGHT THE BOSS IN THE SECOND CASTLE IN YOUR TINY FORM THE SAME AS WORLD 7

you have to beet the level two boss while tiny