3.12 was almost ready in March when I packaged up the version that you now have, however it was only released officially this month.
So essentially you have an almost full 3.12 version on your Bela at this point. If you have 3.12 on your computer as well, this means you will not need to manually install the Bela class files, as they are bundled with Sc as of 3.12.
In the coming weeks I aim to release a full 3.12 build for Bela.