A person adopts there spouses child from a previous marriage. If they devorce does the adoptive parent owe child support of does the bio parent that gave up rights owe child support

Once the child is adopted and the bio parent gives up not only his rights but also his obligations.

The new adoptive parent is not the one who is responsible, they can get visitation and can be forced to pay child support. So a good note, you don't adopt unless you want to be involved in that child's life forever,
Which is what the adoption is, it is saying that not only do you love the parent, but you want to be the dad or mom of the child. With it you get a lot of responsibility and commitment

So yes you as the adoptive parent will have to pay child support, the bio parent is free and clear after the adoption takes place and has lost all rights and obligations

The adoptive parent.