I may be a 2kyu in C, but I feel this is generally an unreliable indicator of the depth of awareness of a coder to any partiucular language. Also, I'm 100% self-taught in coding, so I am constantly filling in various gaps. So, thank you for the affirmation of my supposition.

You are correct; this prompts a warning: format specifies type 'int' but the argument has type 'size_t'.

Hence the warning unsequenced modification and access to 'n', about which I wonder there is a risk of U.B.

Is it because there's no guarantee that one side or the other side of the assignment may be evaluated first?

the tests free() the returned pointer, so the program would crash if you returned an automatic array

I scrolled through some solutions and I can see only ones allocating memory dynamically. What example solution would you think would fail?