Can a girl get a breast reduction from 34H to a 34B, or even better to a 34A? Scars will be similar?

The enormous breast reduction will require maintaining blood supply to the flap. The thickness of the flaps are the limitations mag factor on size reduction. An experienced Board Certified plastic surgeon will guide you.

It is very difficult to give you much advice unless you are examined.  Photos will help us out online, but again it still would be a guess.In general, if you are a true H cup, I would say it would not be possible to reduce you enough to get you to a B or an A cup.  The reason is that some breast tissue needs to be left behind so that the nipple and areola could nourish and live off of.  Without the adequate amount of breast tissue left behind you would loose your nipple and areola.Certainly a very small breast size can be obtained but it really depends on what you are starting with.  Visit with a board certified plastic surgeon and get some opinions.Good luck.

usually still end up being small C cups at best.  So be safe and just let your surgeon know you want an aggressive reduction to maximize your resection and see how you heal.  Then you can decide if a further reduction is really needed or now as you may end up liking your C cup.  If you're huge, consider free nipple grafts and use of the amputation technique to maximize your reduction in one step.

Your question is a good one. In breast reduction, removing lots of beast tissue is very often necessary, and going from an H to a B cup  is possible. In general the more breast tissue that is removed, the more there can be issues with blood supply to the nipple, or possibly issues with poor healing. Without photos or seeing you in person, or viewing photos, specific recommendations are not possible.

Thank you for the question. 
 It is possible to reduce the breasts size very significantly. The concern with the amount of tissue removed is related to blood flow to the remaining tissue; if too much tissue is removed in one operation the blood flow to the remaining tissue (including nipple/areola) may be compromised. Part of the tissue that is left in place is called the “pedicle"; this segment of tissue is responsible for delivering the blood supply to the nipple/areola tissue. If the pedicle is made too small (in the effort to reduce the breasts as much as possible) then patient will likely have problems with tissue survival.  
For most patients in your situation, we have been able to decrease the breast size very significantly and achieve the patient's desired outcome with one operation.  Sometimes, a two-stage approach will allow for safe reduction and achievement of the patients' "very small" desired outcome.  Much of course depends on the patient's starting anatomy and carefully communicated goals.
My best suggestion: seek consultation with board-certified plastic surgeons who can demonstrate significant experience achieving the types of outcomes you will be pleased with. This careful selection of plastic surgeon will be the most important decision you make.
Before undergoing the breast reduction procedure it will be very important to communicate your size goals with your surgeon. Most patients wish to achieve a enough of a reduction to help with their symptoms while remaining proportionate with the remainder of their torso. I suggest that you do not communicate your goals in terms of achieving a specific cup size. For example, a “A cup” may mean different things to different people and therefore may be a source of miscommunication. In my practice, I ask patients to communicate their goals with the help of goal photographs.
I hope this, and the attached link/video, helps. Best wishes.

The only real way to do the degree of reduction you request is with a free nipple graft reduction where the nipple/areola are removed at the start and put back on at the end as a skin graft. This eliminates the need to save enough tissue blood flow to keep the nipple alive on the breast tissue. The disadvantages are permanent numbness, inability to breast feed, and possible loss of the nipple graft.

 Yes, it is possible to get a breast reduction to a very small size but it may have to be done with what is called a free nipple graft technique. This would cause loss of nipple sensitivity and total inability to breast-feed in the future. The scars are the same as The standard anchor pattern breast reduction