Actually, decided to take a look to it, and I think the answer for 1.1 (and thereby 1.2 potentially) may be wrong. That thing is pure pointer arithmetic which should be well defined really

Yes, it should be well defined, but it's not (maybe this has changed in C++11, I've not re-checked the spec). You're allowed to point to "one past the end" of an array, but no further than that.
In practice, it works fine, but a compliant compiler is allowed to do whatever it likes if you ask for a pointer that's "two past the end" of an array.

Actually, decided to take a look to it, and I think the answer for 1.1 (and thereby 1.2 potentially) may be wrong. That thing is pure pointer arithmetic which should be well defined really

Yes, it should be well defined, but it's not. You're allowed to point to "one past the end" of an array, but no further than that.
In practice, it works fine, but a compliant compiler is allowed to do whatever it likes if you ask for a pointer that's "two past the end" of an array.