Hello Aspirant, Now a days Mess has different varieties of Food available a different colleges,you may feel some problems in starting but it will minimise with the time, More over there are many South Indian Restaurant near AIMS Rishikesh like Duglug Restaurant, Koyal Grand Restaurant, Amar Restaurant where you can get South Indian Food,If you want you can South Indian Food  by using Swiggy and Zomato at your room. So, you will not feel much problem in terms of Food in AIMS Rishikesh.