Harry Potter and the Order of the Phoenix?

I want to buy Harry Potter and the Order of the Phoenix video game. My cousins and I have played the Chamber of Secrets game, and what we liked most about it was sneaking out and going on the broomstick. If you know about this game, have this game, or have played this game, please tell me if you can sneak out and/or explore the castle in it. Especially if you have to sneak past Dolores Umbridge or Professor Snape. We want this game preferably for the Play Station 2, so feel free to answer if you know about the game on the console. Also, we might buy Harry Potter and the Half-Blood Prince, and would like to know if it is worth buying, and has the sneaking out, exploration, etc. Thank you! I will give best answer if it is truthful and I can see there was an effort!