Presumably you are talking about SDW (SnapDrive for Windows), not the SDU (SnapDrive for Unix), right?
1. Windows Guest OS in VMware 4.1, running SQL , SDU 6.2, SMSQL, sees ISCSI LUNS direclty from FAS3000 without using RDM. Is this supported?
Do you mean iSCSI software initiator running inside guest VM, talking to a LUN on a filer? I believe it is still supported, yet iSCSI RDM will probably perform better (VMware iSCSI stack is quite good).
2. In the above scenario, if there is a need to have Microsoft Clustering, is that supported? or needed in a VMware environment?
MSCS in VMware is a very hairy topic. The support for it used to be limited to FC only plus few other hefty restrictions (e.g. making VM tied up to a particular ESX host). Having said this, many people were reporting running sucesfully MSCS over iSCSI.
3. With SDU 6.3 and VSC 2.0.1, can I have scenario 1 and 2 above with everything being hosted on VMware datastores?
Well, not really. If you mean NFS datastore, then yes, SMSQL 5.1 + SDW 6.3 + VSC 2.0.1 should work, but a) it has nothing to do with LUNs / iSCSI, b) I severely doubt MSCS will be supported (ever )