how to get older solaris 10_recommended patch clusters??

Guys,
I have an old program which has pretty specific instructions that it requires solaris10u4 and the recommended patch cluster releases in april 2008.
I have installed solari10u4, and my questions are :-

  1. If i upgrade to the latest patch release would have an impact on the performance of the program??? (isnt solaris totally backwards compatible???)

  2. Is there any where i can download the desired recommended patch clusters??

  3. Any help of updating each patch one by one?

Thanks