I took the Turkey tour, and I don't know that it would be any easier or that other tours would be more difficult. It was often easier to get a beer in Turkey than a cup of coffee. Beer, wine and spirits were readily available and at one stop, alcoholic drinks were served to the group. I don't know if all the food was halal.
Vegetarian food is readily available throughout Europe. When you sign up for a tour, you can indicate your dietary restrictions. While halal isn't available, if you can manage with vegetarian or meatless food, you'll be fine.
I don't know what prayer is required. If you need 15-20 minutes at specific times of the day, that isn't likely to happen on any tour - including the Turkey tour. The itineraries are full and while there is free time, most mornings and afternoons are with the group, either on the bus or touring sites. Even the "My Way" tours may not work for you as there are long bus rides.