What does the flag FLAG_ACTIVITY_SINGLE_INSTANCE do here?

Intent i = new Intent();
i.setAction("com.android.MYACTION");
i.setFlags(Intent.FLAG_ACTIVITY_SINGLE_INSTANCE);
startActivity(i);

Options
1) It will start a new activity with matching intent filter, in a new task always.
2) It will start a new activity with matching intent filter, in a new task only if that corresponding task is not in memory now.
3) It will start a new activity with matching intent filter, in old task always. here old task means task in which the current activity is running which has started new activity.
4) This will start new activity in a new task, where only this activity will be there in that task and no other components. if at all new components are launched from this new activity, they will be launched in a different task.