The first error suggest an error accessing a variable, is it the conference app from repo without editing?
The second is harder to debug without inspecting the code nor the console output, maybe an image of console logs and if your fork of conference app has been modified, then we would need to see the code.
The third (though the numbers are wrong) i tested just now with alpha.49 and the error still occurs, doesn't matter if it is a root page nor a nested page.