I am trying to open older part versions in creo 2.0.
It's not clear what you are wanting.
Creo 2 should open creo 2 and older files without a problem.
Can you attach a sample file?
Is it giving you any errors?
Older, as in before Creo 2, or older iteration, as in A.5 is the latest and you want A.2?
Look in the options to open a file.
Please elaborate and clarify your request. It is unclear.