How does it work when you unarchive a process that was completed in an much olde

Hi mathieud, In our case, unarchiving has been done for resolving few issues (instances that were run on 7.6 version are archived onto 7.7 and 7.8 version) in Prod environment and we never saw an issue till date. The instance will look as same, at the time it was archived.

Anyone have experience unarchiving older processes?

A long time ago and as I recall unarchived to the version they were created on. Check with support to confirm