The CBI officers should've worn gloves while investigating in the building where Mahesh Babu was there to shoot.
When Prakash Raj talks to his fellow officer at Nazar's house, he uses the phone on the wrong side(the reverse side) you can clearly see phone screen when he is talking, but that mobile Model is Nokia 9500, it can be used in any direction. In another scene, he opens that mobile like box and speaks directly.