Super Mario 3D Land
Sadly, the first level of this section of the walkthrough was in fact the only one written for for too long, but now there are a marvelously stunning three levels.
Because of the way the wiki system on GameFAQs works, a sub-section of a wiki page can't be successfully linked to until the page is edited again after that section is edited into the page. Because of this, the link to World 2-3 won't work until this page is edited again. Not that those links are all that important, but anyway, the link will be fixed eventually... probably.
Use the binoculars at the start of this level and look up to see a Toad. Zoom in on him and he'll toss a Star Medal over to the top of a cliff a little ways forward. You can get atop that cliff by bouncing up some mushroom platforms in front of it. Between the binoculars and the cliff are three ? Blocks lined up next to each other, the middle of which has a Super Leaf, a Roulette Block, a bunch of enemies that you can ignore or defeat by any of the usual means (Fire Flower, Tanooki Tail, jumps), and some optional moving platforms.
To the right of that cliff is a pipe with a Piranha Plant in it. Defeat the plant and then go down the pipe to get to another grid-like room with a Star Medal in it, similar to the one in World 1-1. As with the room in 1-1, you'll need the 3D turned on in order to easily see the actual layout of the blocks in this room.
In front of the cliff and in front of the pipe, there's a tower-like structure that you'll have to climb up in order to progress further through the level. First, though, if you want, you can step on the P Switch to the left of where you can start climbing the tower to make some Rainbow Notes appear. If you collect all of them, a power-up or a 1-Up Mushroom will appear, depending on whether you're already sufficiently powered up or not.
Once you're on the third step of the tower, you can notice a tunnel in the side of the next step; you can crawl through that to get a 1-Up Mushroom. After that, there'll be some Tail Goombas, and then you can either go up the stairs to proceed with the level or get the Star Medal behind and to the right of those stairs, which you can do either by long jumping to the medal or by walking around behind the stairs.
After going up the stairs, there will be a spot where platforms continually go up followed by one where platforms continually go down. There's no risk of death here, but time your jumps so that you don't fall down when going to the set of platforms that go downwards. After those is a Tail Goomba; this one gives you a Super Leaf if you defeat it.
After this is a set of mushroom platforms. Jump up them and into the warp block to get sent to a floating platform with a green switch. Press the switch to make some Snake Panels appear. Walk across them to get to the area with the flagpole. If you kick the rock to the south of the flagpole (just run through the rock and you'll kick it automatically), a Coin Coffer shows up, which you can kill for a fair amount of coins. To get the golden flag here, hit the green switch to the west of the flagpole, use the Snake Panels that appear to get to a mushroom platform, and then do a large jump (press A as you hit the mushroom) from there to get up to the top of the flagpole.
At the start, you can get on top of the ledge to the right by jumping atop the ledge next to where you start out and taking the Snake Panels to the other side (this also takes you by a ? Block with multiple coins in it), jumping up from the top of the pipe to the right of the starting point, or by taking the pipe itself. If you take the pipe you'll be led to a room that has 3D spelled out in coins, and taking the pipe in there leads you to the top of the ledge that has been vehemently obsessed over in this paragraph.
Once you get onto that ledge, you can press the green button to make Snake Panels that take you back to the same area where they start. This would be useless, but they take you through a Star Medal on the way. However, you can also get this medal simply by jumping to it from any of the elevated parts of the area around it (the Snake Panels or either of the two ledges).
Drop down from the ledge to get to a Paragoomba, another green button that makes Snake Panels appear, and an area filled with poisonous water that acts the same way as lava. Either avoid or defeat the Paragoomba (you can do this with any of the ways you can defeat a normal Goomba), press the switch, and take the Snake Panels over the poison and up to a raised platform with two more green buttons. While going up these Snake Panels you will have to jump once to cross a gap when the panels briefly turn sideways. Before pressing them, if you like, you can jump to the left to get to a ? Block with a Fire Flower in it. You can press either, both, or, if you have the Super Leaf, neither of the buttons and you can still get to the other end of the poison okay; it's to the right of the raised platform, and when you get there you'll be at the checkpoint.
Jump up the steps, and then if you want to you can jump up back to the left and into the small room above the area with the checkpoint to get a clock that adds 100 to your remaining time and a Star Medal. If you have a Fire Flower you can also light the torch here to make a trail of coins to lead you to the room with that Star Medal.
After that, hit the green switch to inspire more Snake Panels to flop into existence. Follow them, but be careful not to fall into the poison as it dips into the poison twice and goes sideways once. While on these panels, you'll see two brick blocks with a clock that adds 10 to your remaining time above them. Hitting the rightmost of those bricks gets you a Super Leaf. After that there are some Paragoombas and a Goomba, which you should be able to avoid or defeat, and then the pipe leading to the area with the finish flag.
To get the last Star Medal of the level, you'll need to enter into the area with the finish flag with a Super Leaf, go up to the bricks to the left of the pipe when you come out of said pipe, and spin to break the blocks. After that, walk through the revealed opening while ducking to get to the medal.
To get the golden flag of this level, activate the Snake Panels, follow them, and then jump off the edge of the last panel over to the top of the flag. If you don't think you can make it because of not getting a running start, bad aim, bad preparation or whatnot you can just jump off the panels and step on the green button again to start over.
You start out on a platform in the shape and color of Mario in his 8-bit form. There are three blocks you can jump into here, the middle of which gives you a Propeller Box. Jump into this box to start wearing it on your head, and when you have it on your head, you can press the jump button in midair to get a good deal of extra elevation - you only get one midair jump from the Propeller Box, though. You can hold the button for a higher midair jump. The three P-Switches here will each give you some coins in the shape of an M; some of the coins show up in the air and for some you'll need to use the Propeller Box.
If you break the brick on the ground on the Mario platform, you'll unveil a wheel. If you have a Super Leaf, you can spin the wheel to get up to a platform shaped the same, but colored like Luigi. There's a Star Medal here, as well as a green clock and a P-Switch that you can press for more coins. When you're done, jump off and aim your fall back down to the Mario platform.
When you're ready, you can jump down to the 8-bit Mushroom platform off in the distance. If you like, you can first jump over to the yellow block with the P-Switch on it to make some musical notes appear and drop through all the notes for a power-up/1-Up Mushroom.
On the mushroom platform, there's another Propeller Box for if you got hit and lost your last one, and if you break the brick on the ground you can reveal a wheel that you can spin with your tail to get to a Red Coin Ring if you have a Super Leaf. When ready, go onto the long ? Block hanging off of the mushroom platform, helicopter jump to the yellow block and the blue block that are stuck together, helicopter jump to the blue block (by the way, if you land on a Paragoomba after a helicopter jump you can helicopter jump again afterwords), then jump down through the coin ring and into the Star Medal before helicopter jumping back up and onto the Paragoomba or onto the yellow block. From there you can helicopter jump over to the blue blocks with the stack of Goombas or to the blue block with the green clock, and then you can jump over to the platform shaped like an 8-bit Princess Peach.
On the Princess Peach platform, you can break another brick and spin another wheel to get up to two golden rings, which give you five coins each, and a Star Medal, and if you want some coins you can use the Starman on the ground to defeat the Moneybags. There's also another Propeller Box here if you need it. After that, take the warp box to get to a panorama of the end of an 8-bit Mario level; the flagpole is the actual flagpole of the level, and if you want to you can get it even more easily than usual by using the Propeller Box. You get a classic sound effect for finishing the level.