1) RTB is currently a mod for Blockland that adds several features. For anything back a long time ago, someone more knowledgeable in Blockland history should be able to answer that further for you.
2) Mission Editor.
3) First I suggest figuring out what most default events do. There are inputs (how the event is triggered, such as a player touching the brick), a target (which is what the event affects, such as the player), and finally the output (which is the event itself, such as killing the player). A simple lava pool would use the event OnPlayerTouch | Player | Kill, or OnPlayerTouch | Player | Addhealth | -10. The check box at the beginning denotes whether the event will execute. If it is unchecked, the event will not happen. The text box on the left is the delay. It denotes how long after the input is put in until the event will happen.
4) Tangible add-ons must have a model (things you can touch; weapons, vehicles, tools). Everything must have some sort of script. Look at other add-ons to get a feel for how it's done.
