You can get the source code for older versions of AdBlock at http://code.getadblock.com/releases and install them using a procedure called sideloading.
Note: We will provide basic support for older versions of AdBlock as long as we still support the browser they are installed in. Sideloaded extensions are not updated automatically.
Here's how to sideload extensions in Chrome, Firefox, and Microsoft Edge. We are very sorry but we are unable to provide older versions of our apps for Safari (Mac & iOS) or Android.