We're getting close to the end, and we've still got plenty of levels to go.
Stage 7-5
The icicles, when they fall, will act as platforms. When they shake, they're about to disappear before they slowly respawn on the ceilings. You'll have to be ready to jump from one icicle to another.
Stage 7-6
For this one, wait for the walking flames to fall after running out of ice blocks to melt, then wait for two of them to get on the bridge above the moving platforms. Toggle the switch and the rest of the ice blocks will be melted.
The switch also reverses the direction of the moving platforms, so grab the key, go up on the moving platforms and toggle the switch when you have fire near the exit again.
From there, you'll want to place one of the magical bridges so that the fire will walk on them and melt the ice blocks surrounding the exit. Place another one directly under the exit, and you're good to go.
Stage 7-7
For this one, grab the key and get in the water. You can use the key to take out all of the underwater enemies by throwing it at them.
You can use a handstand jump to get the purse underneath the exit.
Leave the key there, then use the magical platforms and bridges to make your way to the door. Watch out for the squid when you get back in the water.
Stage 7-8
After keeping the icebergs on the surface of the water, you'll be taking a quick ride on conveyor belts while avoiding a (literally) crushing defeat. Thankfully, the conveyor belts go in the direction where you want them to go, so if you can time your movements perfectly, you can get to Pauline before DK shakes the screen again.
Stage 7-9
Head to the right and flip the switch, and carefully ride to the bottom of the moving platforms with the icicle. Stand on the walrus to trigger the icicles into falling down, then go up and cross the icicle bridge. Just remember that you'll need to walk underneath the spike pit to get the icicles to come down first. Use the magical ladder to reach the nearby switch and toggle it. This switch causes a bridge to appear to your immediate right and also causes the moving platforms to go back up. You'll also open the door blocking the key, so get the key and get back to the start.
Stage 7-10
You'll need to use the icicles as platforms to get to the end. You'll want to run across the second icicle as it's falling. For the ladder before the end, you'll want to get on the last icicle while it's in mid-air in order to climb the ladder, as you cannot grab a ladder while jumping.
The three bonus items are at the end. You'll need to get to them and jump back as quickly as possible; just watch which platforms come down.
Stage 7-11
The invisible door is in mid-air between the magical bridge and ladder icons. It's not exactly between them (it's a little higher up), but it's in that relative location.
Use the magical ladder at the top to get to the switch and toggle it. You can get the key, but there's still the problem of getting to the door. Let the walking flame run out and melt the ice blocks in your way, then drop down from the left and get the magical springboard. Place it in Mario's fall path, and you'll save yourself from falling too high.
If you put the magical bridge where the door is, the game won't let you position the bridge there as it will overlap the door. From there, you can use the magical platform and springboard to get to the bridge. The bridge must be touching the top half of the fourth wall block of the bottom.
Stage 7-12
The icicles make it slightly harder to grab some of the barrels. Thankfully, there are three spots where the barrels will stop moving and stand upright, so you should have plenty of ammunition to hit DK with.
World 8: Rocky Valley
Stage 8-1
Get in the water, grab the key and toss the key up once you're all the way to the right. Go up, plant the magical ladder so that you can climb upwards. Toss the key up over where the hat is. Climb up and get the key before it disappears. If you need to take out the fish, keep in mind that the key will reappear where it is found when it falls into a pit. Avoid the armadillos on the way to the door. You're done.
Stage 8-2
Go to the right, hit the switch, then jump over where the hedgehogs are on the way back. When you reach the platforms, stand on the platforms on the bottom to get rid of them, then throw the key on the conveyor belt and duck to get under the gap. Grab the key, then take the platforms upwards and avoid everything that gets in your path.