Huh? If it worked in Opera, it absolutely wasn’t guaranteed to work in IE < 9 (conservatively; honestly probably every pre-Edge IE). At one point Opera had a more faithful CSS (2) implementation than even Firefox. And nothing guaranteed it worked in IE except checking in IE.

Probably because their model let you customize it for the application.

If you have a Mazda from the mid 2010s, the infotainment system runs in JavaScript on an Opera browser customized for the car system.

Yes, after hitting and/or holding spacebar, something happens, or you change to a new year. Sometimes it's just pictures with some text of whatever was important at that year, sometimes it's animations, sometimes stuff you can interact(?) with. In 1995, there is an old Desktop-PC with Windows 95 booting and starting a modem-connection, and you can type on the keyboard. Pretty pointless, but kinda neat.

Check your ad blockers. I needed to switch off the one blocking the gdpr consent banner

You have to keep the spacebar pressed

That's all I see too: an ugly rendered cassette thing I can spin.

It would be very fitting if it didn't work on Firefox: a sign of the growing enshittification of the Web.