I recommend patients wait 4-6 months before proceeding to tummy tuck. Presumably you had extensive liposuction of the entire torso. There will be swelling/firmness/fibrosis in those tissue for quite some time and can therefor influence the elastic capability of the abdominal skin.
You generally need to keep pressure off the buttocks for 3-4 months after fat grafting. I would recommend waiting at least this amount of time before another procedure.
This depends on how you feel and your blood count etc.If you have good labs and feel good and are fully ambulatory then you can go forward.
You should wait at least 6 weeks. Consult with a board certified plastic surgeon to discuss your options.