You forgot to state the hazard types, and considering the classification you gave it, I'm not sure that a level 4 security clearance is necessary. Maybe level three, at the most.
In the first paragraph of the description you applied a redundancy. You don't need to repeat 'three meters'. For the last part, you can say 'When a subject enters this space' for example.
Of the three descriptor sentences for A, you can combine the last two, otherwise you create a sudden cut-off that disturbs and throws off a reader, ruining the flow.
Once a subject completes six trails
Typo
A will provide subject with food and water for the subject
U wot m8
I like the concept quite a bit, although I question how RPC-259-A doesn't let the ones she takes into the pocket reality die. Maybe for certain ones she takes an interest in after they've succeeded at several of her more difficult trials? There's no real point in demanifesting anything when the person gets wounded because it undermines the danger that they're given. Sure, they'll feel pain, but after a while they'll realize that they can fail however they want since they'll be tended to before they die anyways.
Still, it's at least a difference from every anomaly always killing people, but it's a bit too kind for the spoopy aesthetic that the RPC universe is going for.