Same tabs always open up in Firefox when opening
I have the option to remember my last session in tabs. Mozilla constantly starts with the same tabs. Not the tabs from my previous session, but tabs that I left open in one of my first sessions. It doesn't remember my last session history, and it opens with tabs I left open a few weeks ago.
You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.
Delete the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.
- Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).
Note that your System Details List shows that you have a user.js file in the profile folder to initialize some prefs on each start of Firefox.
The user.js file is only present if you or other software has created it, so normally it wouldn't be there. you can check its content with a plain text editor if you didn't create this file yourself.
The user.js file is read each time you start Firefox and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.