A few things I want to do...

1. Swim - infinite jump while in water? (And if possible, air limit)
2. Spikes where you can die when you touch, like I know in other levels,  you see a red box around the spikes but I do not know how to get that red box.
3. Moving platforms
4. Spike maze (Like a bunch of floating spikeballs, and to navigate, you have to touch objects that will give you extra jump)

1. Not really.
2. Just use the Spikes object in traps. Alternatively if you want the red box method, it's under Invisible.
3. Well, you could set up a complicated system of shifts...
4. You can easily make a maze of spikes, there are floating spiky objects, and... well, there are two types of jump power-up, and you can take them away again but that's kinda complicated.

1. No, but you could exploit wallswimming.
2. Use spikes from a tileset and put bank 16, object 3 on them.
3. Nope. Unless you use a bunch of shifts, and that would slow down movement MASSIVELY.
4. That would be possible, but very complex and involve lots of shifts.

1. See #2
2. See #3
3. See #4
4. See #5
5. KS Source code.

2. See #3

1. See #2
2. See #3
3. See #4
4. See #5
5. KS Source code.

In other words, it's impossible. I don't think it's really reasonable to tell people to make their own mod.

Two is completely possible. The rest aren't