Hi Vijay,
1. You already have RSLinx installed on the server as it shows up as an available OPC Data source (RSLinx OPC Server) in the DA Agent; you also have a DASABCIP OPC Server as well. Please test your queries on both of these OPC Data sources to make sure that the issue is not with the FSGateway instance.
2. I am not sure where the issue is at present.
3. Please execute the query from a transaction and place Event Logging Action blocks before and after the Query so that you can isolate error messages that may be associated with the query if it is in fact throwing an error that NW is logging.
Regards, Steve