It it true that my BMI is meant to be 32 or below to get a mini tummy tuck or a full tummy tuck?

The BMI is just a guide, some surgeons go by it more than others. Some say it must be 30 or lower. However, it should be done on an individual basis looking at all factors of the patient. It is true that in order to get the best result you want to be as close to your goal weight that you can and a weight that you can maintain which will also mean less possible complications in surgery. Be sure to see a board certified plastic surgeon who will be able to evaluate your particular situation. Good luck.

Thank you for the question. Specific calculations, including BMI,  are not always helpful when it comes to determining a specific patient's suitability to proceed with surgery.
Having said that, it is always best (or ideal) to achieve long-term stable weight prior to proceeding with tummy tuck surgery. Doing so, will increase the safety of the operation, will likely improve the outcome of the operation, and will decrease chances that additional surgery will become necessary subsequently. 
In my practice, I do not ask specific patients to achieve a specific weight prior to proceeding with tummy tuck surgery. I simply ask patients to achieve a long-term stable weight where he/she feels comfortable and does not expect significant fluctuation postoperatively.
 Generally speaking, the “ideal” patient for tummy tuck surgery is one who has completed pregnancies, is psycho socially/emotionally/financially stable, has an excellent social support system surrounding him/her, is capable of arranging enough recovery time, does not smoke and who has reached a long-term stable weight.
 My best advice: select your plastic surgeon carefully. Make sure that he/she has significant experience achieving the types of outcomes you would be pleased with.   Then prepare yourself and your support system for a  significant recovery experience (physical and often emotional).
 
 Best wishes.