I've had better results on all my Androids by using 'developer options' and forcing gpu draw.
'destroying every activity' sounds like your symptom, which is to do with RAM and memory.
The password bug still exists in the latest build (on all sites) when entering the text using a 'mobile style' keypad (ABC, DEF etc) the only way to enter a password is to turn the phone to landscape and use the QWERTY keyboard, all other types of input work correctly with the mobile keypad.
Galaxy Note II (Kit Kat)
Note: This bug does NOT exist in 34 beta, so migrating to that unless I find something horrendous 🙂
Can't happen. Some background program must be doing it.
To check, click on the recent apps button. On recent versions of Android there should be an 'x' on each app that can be used to close it, though I think in older versions you could still long-press to get a menu and do it that way. Either way, you can actually close Opera, in which case it won't be able to start itself. If it is still being started after that, some other program is starting it.
I actually mean changing the default text size that a page displays on the screen before any zooming even occurs. Opera Mini has this option in the data savings menu, but it's absent in the full Opera browser.