No, it’s prohibited to install ACs or even coolers in BITS Pilani hostels. There are 2 main reasons for this. Firstly ACs will cost very much and the electricity bills will be high. Secondly, it will be very difficult to provide ACs for around 3000 students inside the campus.
Honestly, you will get used to the heat after the initial struggle and will not even find the lack of ACs a big issue.