Expanding the Amount of Bytes a Level can use:

1. Choose a level which you want expansion. Write the level number down. Now, go into your Windows calculator. Put the calculator in scientific mode, then hex mode. Plug your level number into this equation: BF9C3 + (6 x Level Number). Now, write down the value you get, this is your level address. We will use this number later.
2. Go into your hex editor, preferrably Translhextion. Open your ROM, and go to Jump To-->Offset, and enter x11554A. This is where the free space begins. You'll notice a whole swarm of FF bytes from x11554A to x1201FF. The FF's are unused bytes in the ROM, so all together you have around 44000+ bytes of free space! Now, the first step is that we're going to add object data.
3. To add the object data...start at x11554A (or whatever byte after you do this the first time). Take the offset where the object data starts and write it down, you'll need the offset later. Now, enter thirteen 00 bytes. This represents the header information. After those 00's, enter 85 FF FF. This will put a cloud in the level because if a level doesn't have any objects or sprites it will crash. Now after that, add as many 00's as you wish. Each 00 represents one byte of object data, so place accordingly.
4. Now we will do the sprite data. To do this, skip one byte after your last 00 in the object data, and make sure you leave an FF after the last 00. Now that you have skipped a space, write down the offset, this is your sprite offset. Now, start of the sprite data with two FF's, then after that enter as many 00's as you want for sprite data.
*Note: When you go back to expand a new level, make sure you leave two FF's after the sprite data where the last expanded level ends, or else you will have major problems.
5. Now, go back into your calculator, and plug your object offset into this formula: Offset + 400000 - 200. After you should get a 6 digit number. Now, swap the first two digits with the last two digits. For example. If you got 515B12, swap it to 125B51. Do the same with the sprite offset, and write both of the new values down. These are your SNES addresses
6. Now go into the hex editor, and jump to the level offset offset from way before. Enter your SNES addresses over the first 6 bytes at the level offset (object address first). Now save the ROM in the hex editor.
7. Go into EggVine and open the newly expanded level. You should see a cloud all the way at the top of the screen, plus a new byte limit. Now, you can add your sprites and objects (Just make sure to get rid of the cloud because it's all the way at the top)
To do this again repeat steps 1-7, and remember, every time you do it, leave two FF's after the sprite data of the previous expanded level.

I noticed that cutscenes from SMW The Second Reality Project Reloaded used the X button to teleport.

You can't use that tileset normally in the game. That tileset can only be used in levels in World 6. To change which world you are able to use that tileset in, do the following:

1. Download a hex editor, I suggest Translhextion.
2. Load up your ROM in that tool. At the top of the screen, choose Jump To-->Offset.
3. In the text box, enter x354A. It will take you to that offset. Notice it currently reads "0A." Changing this value determines which world can use that special tileset. Change it to one of the following values:
00- World 1
02- World 2
04- World 3
06- World 4
08- World 5
0A- World 6

Now, you will be able to use that tileset in the world you specified. Now just load up your level and choose Level-->Edit Header, and under Tileset, enter 1. However, note the following:

-You will only be able to use that special tileset in the world you specified.
-This alternate FG replaces the normal grass tileset for that world, so you won't be able to use the normal grass graphics in the world you're using the alternate graphics in.

I don't see why a screenshot is necessary.