JS and React are way better documented than ASP dot net otherwise I would recommend learning that because C# and C++ knowledge is generally more useful than javascript.
I also don't know if FullStackOpen covers multipage sites very well, but it's easy to convert a site later on anyways.
Other than that 10/10 resource that can really help people like the ones described in the image.
Probably not, best bet might be pirating a textbook but even then they really only have options to choose from like Core 3.1 and 4.0 so libraries used in the examples are all likely deprecated.