CPP dynamic memory recovery

I'm wondering how the c++ compiler interacts with hardware in terms of dynamic memory allocation.

For example, when a c++ executable requests memory from the OS, how direct is that access?

If dynamic memory is assigned and then manually reassigned, is it still possible to recover lost data afterwards? Perhaps in OS records or as a result of memory assignment not translating exactly once interpreted by the compiler?

Is it possible to recover dynamically assigned data?