I'll be honest, I didn't find any of these to be particularly surprising. If you've been using C and are familiar with strict-aliasing and common UB issues I wouldn't expect any of these questions to seriously trip you up. Number 2 is probably the one most people are unlikely to guess, but that example has also been beaten to death so much since it started happening that I think lots of people (Or at least, the people likely to read this) have already seen it before.
I'd also add that there are ways to 'get around' some of these issues if necessary - for example, gcc has a flag for disabling strict-aliasing, and a flag for 2's complement signed-integer wrapping.
I'd also add that there are ways to 'get around' some of these issues if necessary - for example, gcc has a flag for disabling strict-aliasing, and a flag for 2's complement signed-integer wrapping.