Question1: Losing data
I think you are saying you did some programming in the T3-LB and after cycling power the changes were gone. How it works is that the T3-LB will automatically store your changes to flash periodically in the background every few minutes. It will also write to the flash whenever you save or load a program so if you are working and cycling power frequently you will want to save the program or manually save to flash before power goes down.
Question2: Not clear but it sounds like you are asking what is register #62 on the T3-LB product. I show its the ID of the subnet device you would like to talk to when doing some subnet operations. The modbus register list is here for reference.
And here’s the view from the Modbus register viewer tool which will be helpful while integrating: