Agrew with other comments- let your dr know it is important to you too.
Yes, many OBs have different ideals for a vaginal birth, but as long as Baby A is head down and there isn't a large size difference between the two you should be able to try for a vaginal birth. The type of twins you are carrying makes a difference as well. If you have mono/mono twins, I believe they usually do a csection. But if you have mono/di or di/di you can have one.
Yes along as they're both cooperating and in the proper position.