Hi Rohit,
You can search about patent expiry for ANDAs on Orange book (for biologicals you have purple book which is available in pdf) which is their USFDA website. There you can type the molecule name and get data about the patent expiry.
I dont have much clarity about when the generic can be launched on exclusivity expiry or patent expiry. Actually, it varies from molecule to molecule. A drug can have various patent and exclusivity expiry dates. Even in exclusivity, there are various classifications like New Chemical Entity, Paediatric drug, Orphan Drug etc and an extension is given in case of any of these classifications (extension beyond the regular 5 years of exclusivity). Also, there can be some agreement which a generic player can enter with innovator eg Alembic has USFDA approval for gPristiq but hasnt launched it yet as per agreement with innovator because of various issues like litigations etc. I usually google about generic entry of a specific molecule. But still too difficult to predict.