Urgent Query in SA's.....!!

IS oly the Revised SA's applicable in certain SA's for this nov xams...? Lik in case of SA 320( Revised) - Should we read oly the revised SA..which is effective on or after 1.4.10 or should we read the original SA also.... 

Secondly CAN ANY ONE TEL IS THER ANY MAJOR DIFFERENCE IN CASE OF EARLIER SA AND THE REVISED ONE>>>?? Say SA 320 and SA 320(Revised) .. .Is ther any new concept to be studied for such cases... Pls reply soon...