Which one is the 4G sim slot in Redmi 3s prime? I have acquired an Jio sim and I am using a Redmi 3s prime. But I don’t know which one is the primary 4G sim slot in the phone. Is it the nano one or the micro one? Or can i choose any one of them? Please help. Thanks
The Redmi 3S Prime uses a hybrid SIM slot which means it accepts one Micro-SIM and another Nano-SIM or microSD card for storage. 

Unfortunately, this means that users will have to choose between a second SIM and a microSD card.

Coming to your question : Use any slot for 4G. It is recommended from my side, use the micro-sim slot for the primary sim.