@clivesneddon You just need to login to Sync to get your data back. Opened tabs from other installations can be found by clicking on the tabs icon in sidebar or by going to opera://activity.
@slytheringirl I had to upgrade my copy of Opera (which I had been avoiding because I despise what Opera has become over the past 2-3 years) as well as reset my sync data to get Opera to let me sign in. This sadly seems to be a permanent occurrance/issue with sync since the devs no longer care to listen to their users and actually fix sync. It's a shame really since Opera is the only browser (after Dolphin killed their Firefox extension years ago) that did sync properly at first, now it's as bad as all the others with syncing to android.
@slytheringirl The message was really from Opera? It could a phishing attempt.
And the fact that you got a message saying that someone attempted to reset your password doesn't mean that Opera was hacked but that someone that knows your email tried to use it to get a new password.