Here is what I am aware about
VIPs and state guests entitled to travel in state aircrafts. Here VIPs can be State Ministers or any reputed position person from any field that serves for State and country.
Yes, officials also travel in state aircrafts but only VIP. Also you will have to notify Office of Director Civil Aviation and Office of Additional Chief Secretary(Aviation) for requirement. These both office can give information of availability and usage of Aircrafts. Different aircraft serves for different purpose. You can contact these offices to get all information you looking for.