The only working solution is to block access to address "autoupdate.opera.com" in your firewall (or add it to the Hosts file if you don't have a FW). I don't know why Opera team is still disabling TLS 1.1 and 1.2 remotely on all clients...
Have you tried the opera:config method noted above in <https://forums.opera.com/post/55410 >? Regardless, some time ago, I also blocked Opera's autoupdater (via renaming the updater file) just to be sure my own settings aren't perturbed any more. As to why Opera continues disabling TLS 1.1 and 1.2, I believe there's a definite though not universal stability problem for some users and sites if those settings are turned on with SSL3 turned off (see: <https://forums.opera.com/post/55555 > plus a myriad of past posts in various forums). I think Opera has set their update server to auto-respond to every Presto Opera startup "ping" with their SSL-TLS fix instructions. In the past, they've auto-delivered JavaScript updates and other things at that startup point, so it's not unprecedented.