@leocg @burnout426 I think I figured it out. I was trying to open the tabs from history in a browser window in which they were not opened before. Does it make sense?

@leocg By following instructions you mean the workflow I described above?

When I go to Settings > History > Recently closed > [Any tab in this list]
The tab I choose opens up in a separate browser window than the one I am on
Why is that and is there a way to make it opened in the same browser window I am on?
Additionally, both right and left click on that tab I want to restore will open it.
Why right-click does an action that is usually for left-click?. Can you fix it please?

Is there a way to sync personal settings across different devices?
For example Extensions.
I installed an Extension in one device but can't see it in another one.

@burnout426 Yes

Re: Can't set as default browser
How do I check that Opera is installed for all users on Windows 7?

In Bookmarks Manager, is there a way to jump to certain bookmark by pressing its first letter?
When I try nothing happens. I have to scroll down the list manually.

I click on Make default button under Default Browser in Settings, however, the question is still asked every time I launch the browser.
Is it something to do with Windows setting?
Additionally, when I click that button, no confirmation message shows up, to say that the new setting was saved. Is this normal action by the browser?