My 2 yrs old always constipated and she poo like every 3-4days. Any recommendation?

You may want to give probiotics, more fruits like banana to help in digestion. It can also be due to less of eating food/less water/more milk therefore your child has constipation. I had it for my first child too. We found out due to milk issue and less food intake. So we make a change and now she can poop better.

Maybe can try prune juice if your child is okay with the taste of the drink.

Take probiotics