More easy questions...

Has anyone ever been able to achieve the same effect as ID in Doom II level 7, ie: the walls lowering when you kill all the mancubi and then the floor rising when everyone is dead?
I've tried loads of times and can't seem to do it at all.
Also, I've seen in quite a few of the Plutonia and TNT levels when you walk into a room or over a certain part lots of monsters teleport into the room. How is this done?
Is EDGE and editor or a port?
Thanks for any help.

EDGE is a source port. http://edge.sourceforge.net

That effect can only be done on map 07. You just give the sectors you want to lower a sector tag of 666. It only seems to work with the Mancubus. I've tried other monsters and it does not work. To make a sector rise you give it a sector tag of 667. Again this only works on map 07 and only with the baby spiders. This is all hard coded into the original .exe. I don't know about the source ports like Boom though. I'm also certain you can do this sort of thing in ZDoom on any level, with any monster or combination of monsters you want via scripting.

Take a good look at the maps the monsters teleport in. There must be a way they can see or hear the player from a nearby room that is otherwise separated from the map (like in e1m9 of doom). So they wake up, move about and cross a teleporting sidedef that leads to the player's area.

Yes, either they wake up when you go into an area or they see you and are blocked by some barrier until the author wants them to be let loose. Usually they "hear" you when you're fighting in the area, and often you'll see a small tube-like connector to their holding area. That tube is often blocked off by using the same texture for the normal and upper (or lower) in that area, so that the hole isn't visible by looking at the wall.

With ZDoom, you'll often just spawn new creatures at certain map spots via scripting. That's much easier to control, and you don't have to worry about the direction of the storage bin, the teleport linedefs, and the player (the monsters will go toward the player, so you have to keep that in mind).

...when you walk into a room or over a certain part lots of monsters teleport into the room. How is this done?
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I've used this a good bit, though I ususally have the monsters
teleport in when you walk into another room and have to come
back, so it isn't easy to see where they came from. Anyway...

I tried to make a diagram but all the spaces collapsed. I
hope this explains it.

You make a room, add a 2 sided line tagged to lower a floor.
Make another room off to the side where it can't be seen,
using the same sector number. Put the monsters there. The
monsters are not deaf. This way, when you fire a weapon in
the main room the monsters hear you even though they can't
see you and you can't see them. Crossing the line lowers
a wall in the monster room which allows excited
monsters to cross the lines of which are tagged to
teleport monsters. That's all there is to it. With ZDoom
you can use the BOOM teleport specials like "no fog" for
different effects.

If you want a diagram I'll put it on my website for viewing.