Hi!
Glad you like the book!
Regarding the questions:
(a) int main() { return 0; } -- yes, this is very important; for a few-mins.-long explanation, see e.g. a lecture (by Richard Buckland, UNSW):
// more precisely, just 30:40-37:00, answering to "Can you use void main()?" ;-)
(b) Bloodshed...