Could someone give me actual coding for 3D scrolling effects like in Super Mario Kart or F-Zero?

You can probably look up Mode 7 in Google. It's a technique that gives the illusion of a 3D plane/surface.

for smilebasic, i mean.

There is an engine on smilebasic source called eZSB. It has some demos and functions for mode 7

I am asking because I can't enter codes for programs! Is eZEB or whatever its called built-in?

No, there aren't any engines built into SmileBASIC. Why can't you download other programs? Anyways, you can still do what I said and search on Google. This will only give you the logic portion you need, which you can then translate into SmileBASIC code.

Online Interactions are disabled. There ya go. Thats why.

Does'nt coding polygons involve commands like GLINE?

Yes. Anything graphical really. Gline, gpaint, gpset, all that stuff