If I remember correctly the sync is going to land at the same time as bookmarks as they go hand in hand well. As for now bookmark manager etc is in beta and developer builds and things are meant to not work perfectly there as that's where we mainly find most important bugs. But as the new bookmark manager is already in Beta, means that it's soon to be ready to go stable

Yep, seems it might be related to a problem with java, but as long as it works in 24 you'll survive for now Java problems are pretty high prioritized so it will be fixed soon I believe

Looks like someone else had the same problem with Netflix, I'll look into it.

I have no idea, didn't even know Opera worked for Chrome book ._.

In another perspective:
Developer is where we add new stuff
Next is where we fix everything that's not working with the new stuff
Stable is the final product.

The final browser is Opera Stable. Which is 24 now. When the Beta(Next) build is finished (It's 25 now), it will move on to Stable and overtake the Developer version. It might be a little hard to understand, but Stable changes to 25, then Beta changes to 26 and Developer becomes 27. 24 is then gone. So in a little current beta will be the Stable version

As in performance you can run a benchmark for it and find out Opera and Chrome are about equal while Safari is so far worse that you don't even want to think about using that browser. Away from that I guess Opera and Chrome win over each other in different areas and the best thing to do is probably pick the browser you think suits you the best.

For me it works fine with the same version and OS. Next time you have a bug you should post it in Opera's BTS (bug tracking system) here: https://bugs.opera.com/wizarddesktop/
Part from that I think this is a you only problem as I haven't seen any other bug reports with the same issues and neither do I have it myself.

That is really weird... Should be back if you reinstall O12 tho, but it might be a pain in the arse to do

You can choose to use the new or the old speed dial at the moment I think this was a silent update, where you'd get it next time you restarted Opera. As there is no longer a "Next" version of Opera they changed it to Beta for everyone.