Will the participants get to pick the free course? 

If not, What if I already have it?

If we can pick one, I noticed there are some courses missing on the H3D site, like 'Learn to Write Unity Compute Shaders' and 'A Beginner's Guide to Machine Learning', Will I be able to pick any of the missing courses? And since I'm already asking, Why are those courses not available on the H3D learning site?

Thanks for your questions! You will be able to choose any course on H3DLearn. Some courses are Udemy-exclusive and while not part of the jam, there may be some exceptions permitted.