1. Click on Add Actor at the top of the screen.
It will prompt you to give the actor a name.
Right click the actor which now exists,
Choose actor control.
There should be a slot with the actor's name.
You need to create a new actor with the same stuff if you want it to have a different name. Editing the name later is a feature I would not mind having.
2. At the start, you don't even need to know code. Try the Game Editor help files for descriptions of what each piece of code means. Also try here:
http://game-editor.com/programming.html
The nice thing about coding in GE is that it's usually relevant and local to each actor, so you don't have scrunch out 10 lines of text to draw a square.
3.
http://game-editor.com/forum/viewtopic.php?t=974
Also, try some of the GED files which use gravity. These can be found here:
http://www.game-editor.com/demos.html
You'll have to look at the scripting for the actors which are affected by gravity.
4.
http://www.macmonkies.com/Fun/DontPanic_800.jpg