reinterpret_cast creating a trivially default-constructible object

cppreference states that:

Objects with trivial default constructors can be created by using reinterpret_cast on any suitably aligned storage, e.g. on memory allocated with std::malloc.

This implies that the following is well-defined code:

struct X { int x; };
alignas(X) char buffer[sizeof(X)];    // (A)
reinterpret_cast<X*>(buffer)->x = 42; // (B)

Three questions follow:

1. Is that quote correct?
2. If yes, at what point does the lifetime of the X begin? If on line (B), is it the cast itself that is considered acquiring storage? If on line (A), what if there were a branch between (A) and (B) that would conditionally construct an X or some other pod, Y?
3. Does anything change between C++11 and C++1z in this regard?