Green Sprouts baby Snap Reusable Swimsuit Diaper, 24 Months +, Light Pink, Piece of 1

Baby wears a size 4 diaper... which size do you suggest?

Can you use these for potty train and how well do they work if so?

Can you dispose of poop and reuse or need to put a new one on each time it is soiled?

What's the best size for a baby who wears a size 2 diaper (almost 3 months, 13+ lbs, chunky legs)?