@fridockshir I've gone down this road and I actually figured out how to stop Opera from updating.
Having gone down that road, what I found is that it's honestly not worth it. You run into two problems:
1 - After X number of skipped updates, you reach a point where your version of the browser stops being compatible with all the things you want to use & access online, especially if you have any interest at all in ever using any extensions or watching/listening to any streamed content at all.
2 - Once you reach that point and you want to update Opera, you have to un-do everything you did to stop the auto updates - and the process of undoing the block is a pain in the neck.
For me, the takeaway was this: rely on browsers where I trust that mandatory roll-out only comes after the development team has adequately tested the new version. You can fight the roll-out, but it's honestly not a battle worth winning.