

It doesn’t look like they’re carrying any weight. If you look at this video of the opening ceremonies, right at the beginning you can see the athletes in the torch not actually touching the level above them.
Longer versions of the ceremony seem to show moments where the acrobats on lower levels both have their hands out into the air, or are even hanging from the level above them - suggesting any given level is capable of supporting both the weight of those below and above it.
3D CAD software. There are a few options out there (FreeCAD, LibreCAD, etc) and Blender is a thing that exists for more artistic 3D modeling. But they simply don’t hold a candle to the features and capabilities of the paid packages, which typically have costs in the 4-to-5-digit range. And I’m not talking the crazy high-end simulation options - those I understand, they’re hard - but basic modeling features.
Hell, I’d even settle for a CAD package that had some solid basic features and had a reasonable purchase cost. Unfortunately the few providers have the industry by the throat, and so your options are “free but terrible” and “you need a mortgage to use this”.