Unfortunately " error 50" is a very generic error code. My experience is that there is an issue with your phone trying to connect to Apple's servers, and its being interrupted. It could be numerous things from your sim card connection, your WiFi antenna, a chip has been fried, even 3rd party app interference (unlikely). Try using wifi to connect to servers and see if that works, then try connecting to itunes via a Mac or pc. Back it up if possible. If some work but others don't you know where to start.
Another thing is you could Try is !Gently! cleaning sim card slot and sim card with 91% isopropyl alcohol and new a soft toothbrush.
In the future rice is not a very good solution because
A. Rice is dusty and dirty
B. Rice in not very absorbent
C. The water isn't usually the main issue, the minerals and sediment that water leaves behind.
Read the guide here Reparación de los daños en un iPhone debido a la entrada de líquidos
Here's a quick overview
If it happens again
Turn off phone right away
Then disconnect the battery as soon as possible.
Remove motherboard and clean the surface very gently, paying special attention to all the connections as per above with isopropyl alcohol and new (or cleaned) soft toothbrush.
I hope one of these help you and sorry if they don't