I'm gonna go with 50% chance model. I think the third model is over complicating it. The person, no matter the day, always has a 50-50 chance of choosing heads or tails. Seeing that they are always unaware of the day, or how many times they have awoken before. They have no basis or enference on how to choose. Therefore they will always have a 50/50 chance. So, even if tails was selected every time and woke up Monday and Tuesday everytime, the person would never know that, therefore they still have only 2 options heads or tails. 50/50.