I recommend waiting at least 6 months after your BBL before getting a tummy tuck. After 6 months, sitting on your butt will not make it more flat as the fat which is in your BBL is permanent at that point. A tummy tuck can make your BBL look even better by cinching in your waist and flattening your side view. Hope this helps!

Depending on your breast implants there is a chance your areola will expand. However this expansion is usually in proportion to your breasts so it usually looks fine. If you feel your areolas may be too large, they can be reduced at the same time as the surgery or they can be reduced during an in-office procedure with local anesthetic only. Hope this helps!

Generally speaking it is unlikely that using an implant only one side will improve the symmetry between the breasts. Implants add both volume and shape to your breast, so by adding an implant only one side, you may restore the volume to match, however the shape will change as well and will likely not look like your natural breast. Fat transfer is more reasonable in increasing volume to match the other side. You may also combine both a very small implant and add fat grafting on top. It is best to have an in-office evaluation to determine the best treatment plan for your breasts.