Hi Lakshmi,
The main thing that 3rd Edition included that is not in 2nd Edition is a set of UI requirements for LMS's to implement. Most of stuff you see in 3rd Edition examples should apply to 2nd Edition as well, but in 2nd Edition you are going to see more implementation variation across LMS's.
Some helpful links:
You can find a high level overview of the differences between all SCORM versions here
You can download the SCORM 2004 2nd Edition specs here.
You can also find a document providing a detailed listing of the changes between 2nd and 3rd Editions here. (look for the Impact Summary)
You can download manifest template files that are correct for each edition here.