How does a for loop work under the hood?

Question presented to candidate: "Forget the syntax for a second. When Python runs for x in something:, what actually happens, step by step? What does the interpreter call, how does it know when to stop, and what does that explain about bugs like modifying a list while you loop over it?"

What a strong answer should cover:

• The loop calls iter(something) once (which uses type(something).__iter__, or the __getitem__ fallback), then calls next() on the result before every pass, assigning the value to the loop target
• The loop ends when __next__ raises StopIteration; the loop catches it, so the user never sees it, and then the else clause runs if there was no break
• It is equivalent to a while True loop with try: x = next(it) except StopIteration: break; CPython compiles it to GET_ITER plus a FOR_ITER / JUMP_BACKWARD loop (END_FOR added in 3.12)
• The loop target is an ordinary assignment: it can unpack, it keeps its last value after the loop, and rebinding it in the body does not affect the next item
• Consequences: a list iterator is just an index, so removing items while looping skips elements; dicts and sets raise RuntimeError if their size changes; a generator can only be looped once
• for works on any iterable, not only sequences: no indexes are involved, which is why it works on files, generators and infinite streams

Code / implementation expected: Optional — rewriting a for loop as the equivalent while loop with iter(), next() and StopIteration.