I can see you don't speak English very well, try to understand me here:
To change the sky, go to Build Game (in the File tab), click on the tab that says Level Settings, click on the square that has the ... in it, right by the Global Script section, go down to Sky, and change it from there. You can even view it by clicking the Preview button.
To make scripts...hmmmm. Well, are you a good scripter? If yes, then just change the .fpi scripts. If not, ask Butter Fingers, Locrian, or any other scripter.
I don't know about your third one, ask the person who made that script or whatever it is.
By the way, Solttu, where (what country) are you from? Because someone around might speak your native language.
GunCell: Chrome Soldier
Arriving in 2007.