Upvote:3
You should consult a lawyer, but let me give you a short answer.
No you cannot legally do this.
It is absolutely prohibited to use a visitor visa to live in the US, and that is exactly what you are trying to do. The brief departures make no difference. Being a minor makes no difference, and nor does being in the custody of a US citizen. Even when you have successfully adopted the child there are still steps to go through for them to legally reside in the US.
I know someone who attempted this, and when discovered he was banned from the US, despite having both a wife and a child who were US citizens. It took the intervention of a congressman to get him admitted again.