1) depends on your study ethics and willpower
2) volunteer = no money, only experiences
internship = can be money or no money, you usually get a school credit for completing an internship.
internship is not only for graduated students, in fact jobs found by graduated studenst is not called internship
3) should be the same as getting a real job, just prepare yourself well beacuse these jobs may be your full time job in the future
4) i am not a female, so i cannot answer that question