Okay, so I skim-read this since the start of it made me think it was your garden-variety humanoid, and it effectively isn't much more than a standard humanoid with a ton of kind of random backstory tacked on.
You've got a lot of small grammatical and mechanical issues that make it difficult to take the writing seriously, but I'll just comment on the containment since small stuff like that can be fixed after you've gotten a more solid starting point.
- Why 10 by 10 meters? That's huge, considering this thing is only five meters tall.
- Site-19 needs a hyphen in the name.
- "all corners in the room" does this include corners on the floor? Or just "places where wall meets wall" and not wall meets ceiling/wall meets floor? Why not just state that the chamber is equipped with standard camera surveillance?
- Why "Raysun X-1 Stun GunR" exactly? What if none are available? Is the Foundation doomed? This thing is supposed to be Safe class; why is so much specificity needed?
- The entire "guarded by / monitoring" last sentence seems kind of like a run on, and the phrasing makes it sound like the stun gun is the thing doing the monitoring. Also, does this poor guy ever get a break, or is he supposed to never leave his post? Why not rotation shifts, or just have someone in an office keep an eye on this thing? Why do we need an actual guard standing at the cell/room?
As far as the description goes…
You have a ton of random stuff in the backstory that really isn't necessary. No one is desperate to know that the prize was a trip to Hawaii. I'm also not entirely sure that the backstory makes sense… Rubiks' Cubes are non-organic, so why would they prototype an experimental organic procedure with something fundamentally unrelated? If anything, maybe they'd use a deceased but still organic specimen, but the whole "let's toss this thing in and see what happens" just seems like bad scientific procedure.
The entire last paragraph of the work just seems too common. There's deaths of the people originally involved, the Foundation comes in with weapons or some other gear, captures the SCP, and that's the kind of recovery story that I tend to see most often with humanoids that were created via human accident. It's also somewhat unprofessionally-written… have you taken any high school AP-level writing classes?
Did you get a positive response on the base idea before writing the draft? Ideally, you'd want to make sure your concept is solid before even thinking about writing the draft.