Assignment of a Singular Iterator

Question

A \"Singular Iterator\" is defined as an:

iterators that are not associated with any sequence. A null pointer, as well as a default-constructed pointer (

Answer 1

Question 2 is: Does working with a result that is "undefined" constitute Undefined Behavior?

Answer is: Definitely Yes. Working on UB is UB.

It seems to run fine for you since it is undefined. It can do anything, this includes working as expected, as well as working not as expected.