When opening an Archicad file from within explorer (windows10) by double clicking on it archicad opens it with the latest version, not the original version eg v22 instead of v21.
As a company we don't always want to upgrade a project, hence it would be great if archicad would give you the option of not loading a file into the latest version of archicad BEFORE loading the file. Unfortunately the only warning you get is when you want to save a project and it tells you then that you will be saving it in another version! Aaaaaargh
That is because the PLN file type is associated with he last installed Archicad version.
Try right clicking on the file name and choose "Open With...".
If the version of Archicad you want is not in the list, then you can browse to find it (and it will be there next time).
You can choose to re-associate an older Archicad program to always open those PLN files.
But as far as I know it is not possible to have version 20 open in 20 while 21 opens in 21 and 22 opens in 22 etc., just by double clicking the file.
One of the forum moderators. Versions 6.5 to 25 Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10 Dell Precision 3510 - i7 6820HQ @ 2.70GHz, 16GB RAM, AMD FirePro W5130M, Windows 10