RE: Rollback to previous version - where are old versions
OK, here's how I did it:
Get the extension called 'V7 Bookmarks' and add it to Opera. That'll let you export your bookmarks as a HTML file. Export it to your Downloads folder or somewhere.
Click on this link:
Download the lower option (not the one which says 'Auto Update.Exe')
If you have Crapcleaner, run that and clear all cookies and stuff. Then use the uninstall option and uninstall Opera completely. Once that's done, run a couple of registry scans to remove any traces of Opera.
Go into your C drive (or hard drive) and look inside the Programs folder and the Program Data folder and manually delete anything which says Opera. Go into the 'Users' folder and look inside all the sub folders. Again, remove anything which says Opera.
Then restart your machine.
Once you've restarted, install the version of Opera which you downloaded from the link above.
Go into your C Drive (or hard drive) and go into the folder called 'Program Files (x86)' Inside there, you'll find the Opera folder. Go into that and you'll see two folders near the top. One is called '40.0.2308.90' and the other is called '45.0.2552.888'.
Go into this latter folder and you'll see a program called 'opera_autoupdate'. Right Click on it and rename it to 'opera_autoupdate.old'. This disables the auto update feature so that you won't automatically get any newer versions than '40.0.2308.90'.
That's you finished with all the folders, renaming stuff and so on, so close them and start Opera. The first thing to do is go to Extensions and install the 'V7 Bookmarks' again. Once that's done, open it and you can import all your favourites which you exported at the beginning.
When you check your Opera version, it will say Opera 45, but it's not. It's Version 40. It will also say 'Version: 45.0.2552.888 (PGO) - An error occurred while checking for updates.'. That's OK since you don't want it to update anyway.
This whole post will probably have taken you about 10 minutes to read but the steps I've described will in reality, take you no more than 5 minutes.
Test it with YouTube and you'll find that they play flawlessly now and everything will be smelling of roses!