Automatic Firefox User Agent Switcher for Version 52.90 (Running on Windows XP)

Hello, I need a user agent changer that will work on mozilla firefox version 52.90 because I use windows xp and winxp does not support higher than firefox v52.90 I know there are free on the market but they are not compatible with this older version of firefox. Features needed: 1) Rotate predefined user agents randomly every X number of seconds or on every new window launch. i.e change it every 15 seconds (I will define the number of seconds) 2) I will copy and paste the list of user agent, one per line (Between 50 and 100 user agents I found online) 3) I will make it work on incognito/private mode. Requirement: The extension must start working automatically when firefox launches. I should NOT have to activate it or click on a button every time I launch firefox. Otherwise it will be useless to me because I restart mozilla firefox as well as the computer automatically and regularly. This project should preferably be completed within 24-48 hours. Thanks