How does it relates to synchronization? By the way, you can already password protect your synced data.
To avoid people having access to Opera and any other software or data in your computer, just use a password to login into your OS and add users for others to use it when needed.
I presume you didn't receive anything on the account listed for the forums here? Usually the sync account and the forum account are the same. (And yes, as a moderator I can see what email address you listed here. Though I won't do so in public, but I can send you a PM if you like.)
The sync works very well... And its quite secure on the top. Just need to following the steps. 🙂 Sorry to say that.. Don't want to be rude. I feel with you.
@javimtso All your data should still be in your system. If you also removed it from there and don't have a backup, then your data, including bookmarks, is lost.