When is it possible to skip a key in Wolf3D/Spear?

I'm trying to figure out, what are all the cases you can skip getting a key in the original Wolfenstein or Spear of Destiny? This can be for one of four reasons:
-A matching floor code alerts enemies behind a locked door
-You can alert enemies that must open the locked door to go after you
-Finding the secret elevator doesn't require the key
-A secret shortcut lets you go without the key

I'm not interested in these reasons:
-Being lucky and having an enemy open a locked door it has no reason to open (it's not opening it to try and reach you for attack)
-Keys that are exclusively required only for optional areas and not necessary areas in the level

In the original Wolfenstein I know of the following cases:

Matching floor codes:
-The key in the wooden area on E3L3 can be skipped
-Both keys on E4L7 can be skipped

Alerting enemies that must open the locked door to reach you:
-Making a double left at the start of E4L2 you can alert the enemies in the wooden area from behind pillars
-You can also alert the enemies in the room with the exit on E6L3, but the place you can alert from is very near the key itself anyways

Using a secret exit:
-You don't need the gold key on E3L7
-You don't need the key in the grey stone area (can't remember which color key) on E5L5

Secret shortcut:
-Finding a Hans Grosse in the Aardwolf maze lets you skip the silver key on E2L8 (though I'd debate calling it a 'shortcut')

But are there any others in Wolf3D and what such cases if any exist in Spear?