Does a tummy tuck operation help remove fat/skin accumulated by pregnancy?

Yes. Fat and skin are typically cut out during a tummy tuck. Muscles are tightened as well. Typically some liposuction is done on the flanks and possibly part of the stomach.
Maybe. A tummy tuck alone doesn't address fat; it simply addresses lax skin and loose muscle. When liposuction is added to a tummy tuck (which is most often the case), then fat can be addressed and a more optimal contouring can be achieved overall. For my procedures, i prefer vaser ultrasonic liposuction for additional contouring of the back and lateral aspect of the abdominal wall.
Yes. A tummy tuck removes the excess skin and fat from the abdomen. Usually the muscles are corrected as well.
Yes. When you are pregnant the abdominal wall and skin get stretched. After the baby is born, the skin and abdominal wall don't always return to the pre-pregnant size or shape. A tummy tuck can fix both of these issues. However, it is important to understand that a tummy tuck is not a weight loss procedure. You should be at or near your ideal weight if you want to have a tummy tuck.
Yes. That is probably the main reason some women have it when completed with childbearing.