1. As said, AC is good during all extremes, whether Rains, Winter or Summer. While in summer you find it cool, in winter, you will realise that it is hotter than outside. In rains, it saves from showers, flowing water and humidity. And hence the premium charges.
2. Bed rolls are invariably provided and remain in the same set irrespective of weather. If journey involves multiple days, the rolls are not renewed. Sheets, Pillow Covers and napkin is given washed and ironed while blankets are used for days along without washing.
3. About...
more... food, I am not aware of for this particular train and opinions are already given.
4. Curtain have been since the inception on Windows in 3AC. For cabins and side seats, in principal provision has been made and the IR is in the process of providing in all the coaches. It would depend on the coach you have been allotted berths in.