Thr iz a trick in passing both levels 4 and 7. You do have to pass both with mini mario. Storing a mini mario in a mushroom house is only possible if you get one every time. Which is close to impossible. Instead go to world 3-A, halfway thru this level, in the water thr iz alwaze a block with a mini mushroom in it. Pass this level with mini mario. Then repeat this level agen wit mini mario, now u should hav a mini mario stored. Go to save this game now. Now it doesn`t matter if u die u can alwaze restart form here, only as long as u don`t resave.
U have to go thru level 2 at the last castle. U can grow n get the fire spitting mario n get to the end u can hit the sand-worm-mummy-thing like this but tha last hit must b with mini mario-with the power-stomp. When u finally do so, tha gate opens n instead of going thru to world3, mini mario fallz thru tha crack n opens world 4.
This has to b dun to open world 7 as well. Except u have to do this at tha last castle in world 5. Beat tha big flower n fall thru tha crack n open world 7.
Also on a smaller note wen ur running thru tha treadmill thingz u have to jump on a spring while evrything iz still moving to get tha coin. Thr should b more springs to come along. Pick it up n carry it 2tha ice. jump ta get on top of tha block n slip thru tha small opening in tha ice ceiling above. Wen u jump u must jump off tha wall up in order to run along tha top of tha ice. Follow that to the end n u will get tha final coin in this level.
U should now have opened all worlds.