Let's start with Point 4. Are they removing Madeleine's tongue? How could they pass her off as their own?
My grandson spent 1 year in preschool here. The staff only speak to the children in Portuguese. Well within that 12 months he became fluent in Portuguese. He now speaks English to the English speakers he knows, and Portuguese to those he knows to be fluent in Portuguese.
Those who read my blog will be aware of something I find to be quite curious. My granddaughter is back in England now and on Tuesday just passed, she started an intensive driving instruction course, spending 3hrs per day driving. She's loving it. Knowing a fair bit about the brain, I would have predicted this was an awful way to learn anything, but it seems the plasticity of her brain at her age has proved me wrong.
Bear in mind that although we know Madeleine was nearly 4, her age in the relevant record showed she would be 3 when left Portugal. From various bits and pieces of evidence, I believe Madeleine was small for her age. (K & G both ended up with a height of 90cm, which is not small, but extremely small, though I think there is an innocent explanation for this.) To someone assessing the situation, she looks much nearer the 3 end of the spectrum than the 4 end.
That means her ability to pick up a new language would be excellent. And all you have to do with English is never speak it to her, and that ability should fade quite rapidly.
Getting a near 4 year old child would be a somewhat tougher proposition, but I doubt someone paying for and risking this exercise would dump the child to start again.