But a code based on several standards, not only on C standard. For example we know, that basic source character sets should contain space (C11 5.2.1), we know t

But a code based on several standards, not only on C standard. For example we know, that basic source character sets should contain space (C11 5.2.1), we know that character constants has type "int" and that character constants represent value equal to the code of a symbol (C11 5.4.4). We know used source character set and we know code of the space character. We can configure specific source character set on the POSIX compatible systems. We know that return statement in the main function equivalent to the call to exit function (C11 5.1.2.2.3), we know that only 8 least significant bits will be used from returned value (POSIX.1-2001 definition of "exit"), we know that INT_MAX should be at least 32767 (C11 5.2.4.2.1) so we sure that the result that we got from "return" statement in the "main" function is positive integer from 0 to 512. Finally if we configure source character set to be sure that ' ' has code 32 we know for sure that we got value 416 in the specified example. So we know for sure answer on question 3 based on the C11, POSIX.1-2017, and ISO 646 standards.