A.The best option is to set up and configure a sharing policy.
B.the best option is to set up and configure a send connector on -sr18.thereafter you should set up and configure a receive connector on -sr18.
C.The best option is to make use of the Exchange Server 2010 schema extensions.
D.The best option is to set up an Edge Subscription file and duplicate the file to the Exchange Server 2003 servers.