POS would be determined u/s 12 of IGST Act and it would be the place where passenger embarks for a continuous journey. i.e. THE BOARDING PLACE OF PSGR (Journey Starting Point)
Here It is round trip and would be taken as 2 separate journey ; i.e
1. Bangalore--Ahmedabad--Pune
2. Pune--Ahmedabad--Bangalore
For first case POS = Bangalore
For Second POS = Pune
Note- It does not matter whether travel is by Air India or Air Asia, or Air Etihad. All that matters is starting point and end point of psgr. :-)
You are most Welcome Jaisika. And I know your exam are just to begin; So All the very best for your exams. In case you want my answer on any specific query you could drop me PM OR mail me OR Facebook.com/taxeffects drop a message there.