Here is what Opera wrote about old browsers:
"...If you can not upgrade to the new browser or do not wish to, your local data will remain on your machine but will not update on the Opera Link server. We recommend that you migrate your bookmarks, so you can still access them through our new service's web interface. You can find the migration tool at sync.opera.com/web/."
So bookmarks which are on an old browser, should be available using the new service's web interface - if I understand them right. But my Opera Mini (java on my old phone) does not allow to synchronize this way - or at least, I don't see how, even though I'm logged into my account.