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Can I access an array element from a pointer to an object contiguous with but outside the array?

C prohibits accessing an array out of bounds even if measures were taken to ensure that what should lie outside those bounds were known:
```
struct MyStruct {
    int x[2];
    int y, z;
};
static_assert(sizeof(MyStruct) == sizeof(int[4]), "Unexpected Padding");
struct MyStruct s;
```
In the above case `y` is guaranteed to be immediately after the last member of `x` because otherwise the `static_assert` would fail at compile-time. Nevertheless any attempt to access the memory in `s.y` using `s.x[2]` would be undefined behavior.

However is the converse true? If accessing outside an array given a pointer to inside the array is undefined behavior, is accessing inside an array given a pointer outside the array legal? For example could I access the memory of `s.x[1]` using `(&s.y)[-1]` since `s.y` is **not** an array?