how to check the version of visual studio code IDE

 Solution: Open the visual studio code and go to help and About as shown in the image.

A popup will show the required details.

How to install previous or older version of extension in visual studio code IDE

 Solution: In this example, will show by installing the salesforce extension pack

Open visual studio code and then go to the extensions icon as shown in image below and search for salesforce extension pack.

Right click on particular extension, then you will get an option to install other versions as shown in image.

Select any version from this and install.

Note: In case if your not getting option to show other versions, install and then try again to change to other version by following above steps.