This is an old version of Geometry Dash, including a save file. Thanks https://www.youtube.com/@n3xtery for finding the save! This repository is only to explain to people how they can download and use the Geometry Dash version themselves, and not as "omg I found the version on my own". All credit goes to https://www.youtube.com/@n3xtery.
First you need to download an Android emulator. I recommend you do download LDplayer, but any Android emulator that has root access and a shared folder should work. After you've installed an emulator, you want to make sure you've enabled Root from the settings of the emulator, for LDplayer you can do this by going into the settings of the emulator and then going to "Other Settings", and then enable "Root Access". If you use an other emulator, you should figure this out on your own.
Next, you need to download Titanium Backup. You can do this by downloading the latest release, unzipping the zip, and dragging the "Titanium Backup (root needed)_8.4.0.2_APKPure.apk" to your emulator screen. It should install automatically.
Then, you need to get the backup file on your emulator. You can do this by clicking on the folder icon in your emulator (make sure to maximize the window to see it), and then a folder will pop up on your screen. This is the Shared Folder, which is also available on the emulator. Open a separate window to get to your Downloads folder, and drag the "com.robtopx.geometryjump-20130908-212943.TiBkp" file from the folder you just unzipped to the Shared Folder.
After that, you need to load the backup. Open the Titanium Backup app on the emulator, press the "Menu" button in the top right and scroll down to "Import backup (.TiBkp) ...". Click on it. You should see a file chosing thing. Press the three bars in the top left and press "File Manager". Then scroll down and choose the Pictures folder. Your TiBkp file should be there. Click on it. Then wait until it's loaded and press "App+Data". You might need to press "Install" and then "Done" when the install window pops up. Wait a few minutes until it has stopped loading. Then go to the home screen and start GD. And there, you have the old save. Have fun!
If your Titanium Backup takes an extremely long amount of time or if the saved levels folder is empty, you might want to try to load the backup again, but this time click "Restore Data" instead of "App+Data". Otherwise go to the homescreen and open GD, close GD (don't go to the home screen but close it entirely), go to Titanium Backup, import the backup using the steps described earlier, and press "Restore Data" and wait a few minutes. Then open GD, go to saved levels and hopefully it should show some old levels. If you have an different problem, create an issue.