5 features Opera Browser did first (2012)

Opera did not invent tabbed browsing. Adam Stiles introduced them on his SimulBrowse browser, later NetCaptor, in 1997.

https://en.wikipedia.org/wiki/NetCaptor

https://www.buzzfeednews.com/article/josephbernstein/meet-th...

And they appear to have first appeared on a browser in 1994 with the InternetWorks web browser:

https://www.complex.com/pop-culture/2013/12/evolution-of-tab...