Hi,
1- yes you can have protein shakes in all phases, just make sure that the one you get does not have any added sugar in it.

2- Phase I snacks are as plentiful as your mind can imagine. anything can be a snack. You can have a small salad and toss in a hard boiled egg. Hummus and veggies is nice too. I'd not eat cheese and nuts together though as thats way too high in fat. I take 1 oz of cheese as a mini snack.....1 tbs peanut butter on celery is another good one. I've been having 1/2 cup cottage cheese lately with chopped fresh veggies on top.

3- I do a lot of pre-cooking meals to freeze for easy access. I like to cook up a bit pot of chili for easy lunches along with chicken veggie soups. I also grill up 2 lbs of chicken breasts each week for a quick toss into a salad. It really depends on your life and what's easy for you.

Hope this helps!!