Kadra -
TestStand 3.0 will run the TestStand 2.0 sequences just fine. TestStand 3.0 only added new features. For a list of differences between TestStand versions, look at the release notes for TestStand 2.0.1, 3.0 and 3.1.
The only behavior that will be different is that the file will be marked as modified when opened in the 3.0 sequence editor because the newer versions of the NI types will be used.
Scott Richardson
https://testeract.com