Who will get the custody of two and half years old girl child and up to what age?

If the parents are married to each other part of the divorce is the creation of a parenting plan dividing time with the child. If the parents are not married a parentage action has to establish the father as a legal father after which a parenting plan is created. Unless there are specific reasons why a parent can't have contact with a child (e.g. s/he has abused the child) each parent gets some contact. In WA custody within a parenting plan is relevant only for federal issues and other states. If the parents are unmarried and there is no court action the mother has custody as the father is not a legal father until the court has established him as such.