A rectus diastasis, which is a gap between the rectus abdominus or "six-pack" muscles, CAN be fixed through a c-section incision if your plastic surgeon can do it - it's not easy get up to the ribs through a smaller scar, but it definitely can be done. If your skin quality is great but you have a pregnant looking bulge, this a great procedure for you.
To get the terminology straight, a "full abdominoplasty" means that the scar is long, and that there is a scar around the belly button. Technically speaking, all the skin between the pubis and the belly button is removed, and the upper abdominal skin is pulled down and looks a lot better. Usually a plication is just automatically part of this procedure.
A "mini-abdominoplasty" just addresses the skin between the belly button and the pubis, so it won't improve the skin on your upper abdomen at all. It can still be used to fix the lower muscles, or the whole rectus diastasis. So when you talk abdominoplasty, either mini or regular, you are talking about the amount of skin removed and the scar more than about the way the surgeon deals with the rectus muscles.