Please make sure to finish all your posts before this time. The downtime should only last for a few minutes.
Opera 12 bookmarks to Opera 25
Will they transfer, or I will have to manually do it ?
You better back them up nonetheless. Not in .adr though...
It seems they say you might need to have your old Opera be your system default browser, then heed the process/options while installing (they say it might acquire stuff from the existing Opera on the initial install, providing the old version is a default browser).