[Q] Need some information about I9502 (Samsung galaxy S4 Dual) topic

I had purchased an I9502 through olx.in, last week.
Second hand.
Due to rare users, there is no dedicated thread on XDA for my device :(


Now, many questions arises.

1. I had updated to official lollipop (5.0.1), by SAMMOBILE's official ROM. After upgrading, my second SIM cant connect to network. So I revert back it to KK (4.4.2). Still the problem persists !!!!! . I couldn't use it as a dual sim phone :( Is PDA and CSC version is important while flashing? or we could install any PDA/CSC rom version on samsung phones? I don't know the original ROM so, I had downloaded all firmwares available at sammobile and tested. only 2 of them managed to register my SIM(first) on network. Is it a hardware issue? or by a wrong ROM ? anyway now my mobile admitted at hospital and specialized doctors have been studying his disease :p