Opera blocked by OSX 10.8.5
You could install 10.8.5 clean on an external drive and just install the opera version you hope to use and test in a clean os. If that fails, you’ll know the program opera had a timer of sorts and can pursue disabling or modifying opera. 

If it works, you can then migrate all your settings / apps / data (except opera) to the new os and test. Then restore that image over the broken internal install. 

Splitting the troubleshooting up will save you time isolating and testing without risking your current setup that you wish to remain without an upgrade for reasons.