it seems possible to have multiple versions installed concurrently if they are installed in the different directories.
however, what I do not understand is the mechanism of switching between the versions. there must be some sort of configuration or environmental variable which would instruct which version to use…
Hi @lazar, if you have two separate standalone versions of PsychoPy, they will operate independent of each other, so all you would need to do is run your task and the correct code for that version will be compiled and run. That is, if you designed your task in Builder. If you have manually coded your experiment, then it should also run, unless something has changed in one of the modules.
There is the useVersion function (psychopy.useVersion()) which you can use to control which version of PsychoPy is used to run the task. IF you are using Builder, you can set this from Experiment Settings > Use Version.