the answer of one of the question in the first level is wrong

Question

the function called by libc++ is NOT nessesarily be main. we usually use main as "entry point" called by the initialize routine of libs , but the name can be changed.

Answer 1

The "main" function is the entry point for console programs that is not specific to any compiler. (_tmain e.g. is Microsoft specific as far as I know)
There are also some other "problems" with some of the explanations in SoloLearn C++ but it still might be a good entry point to learn C++. There's just much more to learn about C++ and also a bit to revise later on.