welcome to Health care magic.
1.Ultrasoun is only investigation of choice for fetal anomalies at present time.
2.No
radiation / side effects documented till date - easy accessible tool / cheap.
3.Doctors will check in to each and every structure / organs in the fetal body.
4.Brain and its anatomy, chest, heart - all chambers, vessels,
liver, stomach , kidneys,bladder,bowel and so on.
5.Yes every tiny defect can be seen on
ultrasound - it gives almost 97% accuracy.
6.Good your girlfriends
pregnancy doing well - followup necessary in your case - good luck
Hope it helps you. Wish you a good health.
Anything to ask ? do not hesitate. Thank you.