Recently when I'm working in Illustrator (v. 25.4.1) which I access through a shortcut on my desktop, and I open a second AI file that is saved on my computer, the saved file opens in a second/another session of Illustrator (v. 26.0.1).
I wonder if in the most recent update (whenever that was???), if the program was updated but it didn't replace/delete the previous version of the program. And now when I open a saved file, it opens in the most current version -- not the version that I'm working in.
And if I'm correct, what do I do? Do I uninstall v. 25.4.1? And can I be confident that none of my saved files are affected??? Is there any reason to keep v. 25.4.1 and NOT run v. 26.0.1 (because of bugs, glitches, etc)?
Sorry about the trouble. By default, files open up in the latest version install & when you update the app, it uninstalls the older version first and then installs the latest version unless in Creative Cloud Preferences > Apps you have unchecked remove older versions for that specific app.
I will suggest you to keep both versions as it can come in handy if some issue occurs in the newer version.
For your file opening issue, you may try the following steps:
For Windows only: Right-click on the file > Open with > Choose another app > Select Illustrator 2021 or 2022 (which you want to make default) > Check the "Always use this app to open to open xyz.ai file". If you are unable to locate it, then you may scroll down and click on "Look for another app on PC" > A dialog box opens with Program Files folder > Adobe > Illustrator 2021 or 2022 > Illustrator 2021 or 2022.exe > Click open. 2. For macOS only: Right click/ Ctrl+click on the file > Get Info > Open With > Change Deault app to Illustrator 2021 or 2022 from drops down menu > Change All. If you don't see the version of Illustrator you want in the drop-down menu, then click on "Other" from the drop-down menu > Dialog box will open with Application folder > Look for Adobe Illustrator 2021 or 2022 folder > Double click to open it > Adobe Illustrator 2021 or 2022.app > Click on Add > Change All.
Now the xyz.ai files should open in your desired version of Illustrator. I hope it helps!