One of the issues I've had with Opera was that it had no reset button/option like most browsers do. I was going through the settings a few days ago, I think I was fooling around with the background themes and wallpapers, and I noticed something new.
I don't know when Opera added this option but it's finally there. A RESET button.
Alt + P is supposed to open the settings page, still not working on mine so: Go To Menu top left hand corner and then Settings or type about:settings into the web address bar.
Go to Browser on the left hand menu and on the right scroll down slightly and you'll see Reset Opera. Click on the Reset browser settings... button
and in the next box that opens just click on the Reset button and that's it.
Atl + P Not Working
When I use to go into the settings I used the keyboard shortcut Alt + P but for some reason it just stopped working. Not a big issue but I decided to dig around the Internet for a solution. I ended up at Opera's own forum.
I had signed up before but seemed to have misplaced my sign in info so I decided just to sign up again. Like a lot of forums you don't need to sign in to read them but only if you want to post a question yourself. Scanning through the forums I couldn't find any solution listed. So I posted my question and the next morning I got a reply.
I had to go to Settings. Click on Browser on the left hand menu. And find the Shortcuts section. There I had to click on the Configure shortcuts button.
I scrolled through the list of shortcuts to find the Open Settings options. I noticed 2 shortcuts listed Atl + P, and Ctrl + F12. I first tried the Reset all button, didn't make any difference. Ctrl + F12 did work. So I decided to delete it first thinking it was overpowering Alt + P. That didn't work either. So I reset it again and have to use Ctrl + F12 instead.
Just hover your mouse over a setting and you will see options like Type a shortcut (to set your own) or a X on the end of each shortcut to delete it. And a Reset all button towards the bottom if you want to set defaults.
I was so use to Alt + P that I tried to make that work first. So now it's just a matter of remembering Ctrl + F12 instead. Funny thing is I have Opera version 28 on my system as well and the Alt + P will not work there either. Even though it is the only one listed in their options and is not configurable. No configure button anyway.