I have diastasis recti, how can I get a flat stomach? Will liposuction be enough or do I need a Tummy Tuck?

Hello and thank you for your question. The best advice you can receive is from an in-person consultation. If you have a diastasis, then you are likely a better candidate for a tummy tuck with liposuction.  This can be done through a low and short
incision, all completely below the bikini line. 
The belly button can be designed to look natural and have no scars on
the exterior.   Your muscles can also be
plicated resulting in a flat abdomen. 
Make sure you specifically look at before and after pictures of
real patients who have had this surgery performed by your surgeon and evaluate
their results.  The most important aspect is to find a surgeon you are
comfortable with. I recommend that you seek consultation with a qualified
board-certified plastic surgeon who can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

Thank you for sharing your question and photographs.  Once you have reached your desired goal weight I think you will most likely be a full tummy tuck candidate.  This will allow for repair of your diastasis, effectively cinching your waist smaller, while remove the greatest amount of skin and adipose tissue.  Be sure you have finished having your family and do not have further plans for pregnancies.  Best wishes.