Ctrl+Tab in the current version of Opera cycles tabs with a tab preview. Ctrl+Shift+Tab cycles with a preview in reverse. 1 and 2 cycle tabs without a preview. Any of these may be changed inside the keyboard shortcuts area like I mentioned above.
Have had the same issue with Online Armor firewall. Started with 29, went away with 30, but came back with 31 and 32. With OA enabling 'Learning Mode' for one opening of Opera after install seems to fix the problem.
they are all pretty standard extensions. Ad Block, Bookmarks, Fastest Gmail Notifier, and Gmelius. Sometimes opera will crash and restart once or twice and then everything will be OK. But sometimes it cycles a half dozen times (really annoying) and then all my pinned tabs are gone and the extensions are off and I have to rebuild everything. never happens in windows 7 with the same setup.
Then you can go opera://flags/. Type that to the address bar. Find the option 'Show domain when entering full-screen mode' and turn it OFF. Then that warning is NOT shown anymore, when you go fullscreen.