How can projects created in older versions of Unity Pro be opened and modified by a newer version? How can the project be saved so that it can still be opened with the old version of Unity Pro?

FAQ000233729

08 April 2022

Open with "keep project version" selected.
Project version
Modify program, but do not use function blocks only available in the new libset, or new DTMs. Keep libset version the same as original. 

Libset version
Save project as an archive (.sta).
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