• Changing the loading screen when you load the map.
• Changing what the screens in the elevator room appear as. - Fixed: thanks, guys!
• My map has mysteriously turned fullbright when there are plenty of lights about since I added an elevator. - Mysteriously fixed itself.
• Creating and controlling orange portals using prop_buttons.
• Removing the potato and the ability to place both portals from the portal gun. - Fixed by screwing regular solutions! Eventually found I that I could remove the think function from the logic_script in the arrival-departure ent.
• Linking a prop_floor_button to a timer in the same way a prop_button does. - Fixed-ish. Solution seen in third post.
• Music! GLaDOS! Testchamber signs! Other things! - Fixed, except the test chamber sign just says "00" and "None".

+'s means it's fixed, btw.

Actually, I could probably do that last bit myself with a tutorial. Any reccomendations?

If anybody can answer any of these questions, I will be very happy.

RU.

1. No idea.
2. Put the instances/transitions/arrival_departure_transition_ents.vmf instance anywhere outside of the playable area of your map. For $arrival_video and $departure_video in the instance properties, replace the question marks with a file name from your portal 2\portal2\media folder. make sure to type media[INSERT FILENAME HERE]
3. Open the dev console and enter mat_fullbright 0. If that doesn't help, I have no idea.
4. Use the prop_portal entity. It's not hard to figure out from there. If you want a frame around where the portal will appear, make a prop_dynamic with models\props\portal_emitter.mdl set as the model. Change the skin with inputs and outputs when a portal appears.
5. Probably the easiest way to do that is to put a trigger_weapon_strip in the entrance elevator so that the player loses their portal gun right as they spawn there. Put a weapon_portalgun with the keyvalues changed as needed right on the floor of the elevator pod so the player picks it up right after they lose their original portal gun.
6. Use the OnPressed and OnUnPressed outputs of a floor button similarly to how you would use the OnPressed and OnButtonReset outputs of a prop_floor_button. It shouldn't be too difficult to figure out from there.
7. Music? Use the ambient_generic entity with a sound name specified. While browsing sounds, set the filter as music. You will find a suitable sound file in no time. Set the sound to play using inputs and outputs. Stopping some looping sounds, which would include music, is glitched, however.
   To make GLaDOS talk, I think you just have to use ambient_generic again. Previewing voice files doesn't work for whatever reason, but they should play in-game. Again, set the sound to play using inputs to the ambient_generic.
   As for test chamber signs, that's an instance. Use info_sign_sp_dirty.vmf or info_sign_sp_clean.vmf

Anyway, I hope that helps a little.

On Floor_Button_1:

OnPressed>Timer_1>Start>Delay 0.00
OnPressed>Tick_1>Check>Delay 0.00
OnPressed>Logic_Branch_1>SetValue 1>Delay 0.00
OnPressed>Timer_1>Stop>Delay 10.00
OnPressed>Tick_1>Uncheck>Delay 10.00
OnPressed>Logic_Branch_1>SetValue 0>Delay 10.00

On Floor_Button_2:

OnPressed>Timer_2>Start>Delay 0.00
OnPressed>Tick_2>Check>Delay 0.00
OnPressed>Logic_Branch_2>SetValue 1>Delay 0.00
OnPressed>Timer_2>Stop>Delay 10.00
OnPressed>Tick_2>Uncheck>Delay 10.00
OnPressed>Logic_Branch_2>SetValue 0>Delay 10.00

The timers are set to 10 seconds and are linked to the indicator lights, and there is a usual logic_branch_listener for the door when both branches are at 1.

This, surprisingly, works. However, there are a couple of problems. The timer makes no ticking noises, and - more importantly - if the button is pressed again before the timer is over the image resets but the 10 seconds does not, so it cuts to off before 10 seconds are up.