I think you need to do a lot more reading and research on web services, so I'm just going to give very short answers to point you in the right directions.
when we use rpc? and when we use soap?
There is no direct connection between the two. RPC means Remote Procedure Call, for which SOAP can be used, but doesn't have to. SOAP is an XML dialect used for web services.
Is it possible use SOAP without WSDL
Is it possible to use RPC with WSDL
See above. WSDL has nothing to do with RPC directly. WSDL can be used with SOAP, and SOAP can be used to implement RPC, so the answer is yes.
DIFFERENCE BETWEEN RPC USED IN WEBSERVICES AND GENERAL RMI TECHNOLOGY
WS (as the name implies) use web technology, specifically HTTP, which is standardized, widely deployed and well understood. RMI implies Java on the server, and JRMP or IIOP as the protocol. Oversimplifying outrageously, RPC over WS are more widely usable, and more easily deployable than RMI.
Oh, and please don't shout at us in all-uppercase letters.