I have a bunch of old audio recordings from version 1.2 and 1.4; the new version 2.1.2 gives an error when reading these files (reg compatibility).
Is there a way to revive my old recordings (of course needless to day i did not export them to mp3 at that time)
Have you read the message carefully? It should say that Audacity can try to open the 1.2 projects, but suggests you make a backup copy of them first.
To make a copy of the projects, create a new folder, then copy the AUP files and _data folders into the new folder. It is important you do not make the copies into the same folders, or you may corrupt the projects.
Alternatively, open the old projects in your 1.2 version of Audacity, export one WAV file for each track, then import the WAV files into 2.1.2 and save as a new project.
By the way: there has never been an Audacity “1.4” release.