Fragment: which callback invoked when press back button & customize it

I have a fragment:

public class MyFragment extends Fragment{
     ...
     @Override
     public View onCreateView(...){...}    
     ...
}

I instantiate it:

MyFragment myFragment = new MyFragment();

I use the above fragment to replace the current fragment:

FragmentManager fragmentManager = activity.getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();

// replace fragment
fragmentTransaction.replace(R.id.fragment_placeholder, myFragment, "myTag");

// NOTE: I did not add to back stack

Now, myFragment is showing on the screen. NOTE: I did not add myFragment to back stack.

My two questions:

1. If now, I press mobile phone back button, which fragment's life cycle callback will be invoked??

2. How can I customize the back button click listener in MyFragment class? (please do not suggest me to do myFragment.getView().setOnclickListener, but do it in MyFragment class)