@r1b3r0 When you first enable icloud syncing all current settings will be uploaded to icloud.
Cookie then checks for updates at launch. It will also be notified when a preference has been changed on another device, and update accordingly. Any Chnges to preferences will also be uploaded to icloud immediately.
Cookie has NEVER been working correctlly with firefox, made me loose countless productivity time by multiples bugs : corrupting my profile, my extensions, it breaks history, and even breaking the browser (yes some websites doesn't work until you rebuild your database). I made multiple reports here just to see versions over versions with "fixes" that improves nothing. At the end, i just let firefox managing cookies as i m tired of reporting and loosing my profile and history again and again. Makes cookie useless since firefox is my main browser, actually i wish i can get a refund.
So long story short : if you need firefox browser working, stay away from cookie until the dev makes serious work AND tests to provide reliable software that doesn't break your browser. I have enough of chasing database corruption in firefox after cookie "cleans" it, it's going on for months if not years.
If you use the version from my store, there’s an option to check under the help menu, or on the updates tab in preferences. For the App Store version, you need to check the updates tab in the App Store.