C free() routine and incremented array pointers

Question

Will the free() routine work if I dynamically allocate an array and then pass, not the initial pointer, but a pointer to the middle of the array? Example:

Answer 1

No

(And "Yes", you do need to "set it back".)

The API requires that you only pass to free() exactly what you got from malloc()¹.

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^{1. Or a null pointer.}