What is ''in beta''?
I want to learn Hindi and I've just started. But it's in beta yet, so do I better learn later? I mean will the new subjects be added afterwards?
"In Beta" means that a course is available to desktop users (but not for mobile users). It is when the contributors improve the course should people report any errors. They don't add new topics; they only add new topics when they release new versions of the tree.
It actually does not mean it is available for desktop only; that is separate. It means the course is new and the errors reported per user rate has not dropped below a specific threshold for an extended period of time. I think the Japanese and Korean courses were only available on mobile for some time before being released to desktop.