hi indiescore,
not sure if this helps, but i was able to open a couple of 5.5.5 projects with v5.5.2 and 5.5.3. I didnāt get any error messages on opening. On saving it did mention the version discrepancy and hit me with a prompt about saving a ānew versionā, or āoverwritingā.
note: they were pretty simple projects - not sure if thereās possibly some new functionality in 5.5.5 that I hadnāt employed which might give you an issue if opening in an older versionā¦? (i.e. - attempting to open a 5.5.5 in 5.1 gave an error about some corrupt data).
also: iām on a mac so not sure if a pc would react differentlyā¦?
meant to add: i donāt have 5.4 so couldnāt try that specifically.
good luck!