Firstly about surgical technique. Breast lift and reduction employ similar surgical technique, it's just that with reduction you're removing more breast tissue (because the biggest aim of a reduction is.... to reduce the size of the breast). Does breast lift remove SOME breast tissue, the answer is yes, but the AIM of the lift is more to restore the youthfulness of the breast. Both women, one wanting a reduction vs a lift need their nipple/areolar complex repositioned "up". Only the woman wanting a reduction need the volume addressed.
Furthermore, The Effect of Study design Biases on the Diagnostic Accuracy of Magnetic Resonance Imaging for Detecting Silicone Breast Implant Ruptures: a Meta-analysis (2011) reported that the breast-screening MRIs of asymptomatic women might overestimate the incidence of breast implant rupture. In the event, the U.S. Food and Drug Administration emphasised that “breast implants are not lifetime devices. The longer a woman has silicone gel-filled breast implants, the more likely she is to experience complications.”
Fat transfer breast augmentation has a few important limitations. First, fat transfer is typically limited to approximately one cup size increase in breast size. Second, the transferred fat may be absorbed again by the body. Third, it is more expensive because of the extra time involved in harvesting and processing donor fat as well as possible need for a special vacuum bra device. This option is best reserved for women who desire a modest increase in size without using an implant.
For the second part....it depends where your butt is starting at. There is a point in which there is too much pressure in the butt that no more fat can really be injected. Pressure kills the fat cells (which is why you cannot sit on the butt for a few weeks after surgery). It also means that we cannot just keep injecting if the gluteus has fully expanded and is not able to take any more. If you are starting with a small butt.....there is a smaller limit. If you are starting with a medium sized butt.....there is a bigger limit. I like to use power assisted "vibration expansion filling" to really push the boundaries of how much fat can be injected into the buttocks. This helps to expand the buttocks on the table and get more fat into more stubborn areas. Typically, even for smaller girls, I will inject at least 1000ml per side (and up to 1600ml for larger girls). After this, as you have probably read, 30-50% of the fat will either reabsorb or "not take". However, with the removal of a large amount of fat around your midsection combined with careful technique and contouring of the butt and hips, we can make a very large difference in your overall proportion. Best of luck to you!
Deciding how much fat to transfer to a patient’s buttocks is a decision made by the surgeon that takes safety, cosmetic result, and patient’s goals into account. I recommend reviewing your goals of surgery, by showing photos, or performing Vectra imaging in office, with your surgeon and listening to their recommendations for the safest, best-looking results possible.
It is certainly possible to lift a breast without changing the volume or removing any tissue, however, the breast will sometimes appear smaller after this procedure due to its position. It is also possible to reduce breast volume without lifting the tissue (usually via liposuction) but all reductions that are performed by making incisions will also include a lift.