Per 
Idea: A portal to a universe governed by the laws of Minecraft.
There are two possibilities: One, the whole world looks and behaves exactly like Minecraft, which means the Foundation will not be able to properly influence the code of the world in order to affect anything, people will be cut by sharp edges of pixels, they'll have no surface friction on any of the world's matter, it'll be a no-oxygen world, and probably it'll have no proper mass to create the force of gravity. This will be difficult to manage because I intend to make this SCP dangerous, with entities capable of leaving through the portal like they can with nether portals. If they can't recognize any of the outerworld things: first, they won't be able to be killed because they won't recognize noncode attacks and won't lose hitpoints; second, they won't recognize noncode matter and will probably fall through the earth if they step off the portal; third, they probably won't know which way is down, and they won't have inertia with the Earth, so they'll shoot away into space, and the portal will also be not anchored relative to the earth (probably an omitable issue, we can have them fall toward the center of the Earth and anchored relative to it, but there's no code to tell them that, if you stick with technicality).
Or two, the world behaves like the regular world but shaped like Minecraft, with a tendency toward cube shapes in the matter and the Minecraft entities and magicky things, but otherwise oxygen, friction, gravity, and non-sharp edges. My current plan is this one, with the blocks recubing themselves when no solid matter (sticking with that hard scientific classification, even though my chemistry teacher would say most separate classifications in science have fuzzy lines) of significant enough size (size of a pixel maybe? 1/16 x 1/16 x 1/16 meters) is within some distance (size of a light source is 16 meters, should be convenient enough distance; convenience is important because I plan to make other SCPs similar to popular things, maybe even making a GOI responsible for producing things, and they wouldn't want to make it so hard to use), but crumbleable when outside stuff is close by.
As for the portal, I don't want it to be neutralizeable, but it can be just very tough. It could be bedrock, in which case it wouldn't even crumble and would need metal corner guards to keep people and things from getting severely cut. It would be very very smooth, but dust might create some friction. Treat as ice rink friction levels. Probably would have a ramp up to the level of the portal, or the top of the bottom block of the portal being in the ground. Portal location: possibly underground, although I wouldn't want it to be impossible to discover. It was originally named Cave Game after all, wasn't it? Some spelunker can find it, or reports of monsters from the portal. Will be anchored relative to center of earth and its orientation, facing north-south.
Version has yet to be determined. The estimated time of creation must be concurrent with the version. I'm not so familiar with 1.12. I'm probably most familiar with the features of 1.8. So let's do 1.8.9. There was a big gap of time between 1.8.9 and 1.9 versions anyway.
For containment: Dimensions will be the same as a nether portal (minimum size), so the main SCP-xxxx, the portal, will be 5m tall x 4m wide. Harmless particles will be emanated, as well as sound to a radius of 16m. Containment might not bother about the sound, but soundproofing will not help, so they might. It's going to be anchored relative to the earth and it won't just appear in a containment site, so they'll need to make a new place for it. It won't be close to towns, it will be in a cave, but it will be capable of releasing very dangerous entities, so it probably needs a site. People won't want to work around the sound for hours and hours, with it repeating a brief loop continuously, so they'll probably have low-traffic rooms in the sound radius. Protection on the other side of the portal might negate the need for real-world containment, but the SCP will have necessitated a site in earlier stages and they won't go to the unnecessary trouble of taking down the site because it's contained for now, although budgets may make it become very low-staffed when it becomes low-priority.
Entities will be tough. On the other side, three meter thick wall of obsidian with a water layer within should block everything. Good lighting should keep things from spawning within. To be continued
