TO GET RESOLUTION/EFFECTS SETTINGS ETC.
1) Go to settings>region&language
2) Change "Display language" to "English (United States)"
3) System Locale and other settings will also change, you can change these all back to where you are/language you w...
Hmm, I am using the Play theme http://forum.xda-developers.com/android/themes/theme-twrp-materialised-dark-light-play-t2915584 which works without a problem on my LG-G2.
Could it be a problem on the OnePlus 2?
Do not use a theme on the OnePlu...
Don't know about the headphones issue, but the OP2 only has one speaker. (the one on the right of the charging port)
The other grill is for symmetry (and possibly the microphone)
I think, that the previous owner, perhaps was not the previous owner. It's probably been stolen or found. the actual owner has notified his/her network (o2?) and have gotten the phone blocked. Nothing you can do i'm afraid, it will still work outs...
all that means is MAGLDR is trying to read the android kernel from the SD card, but, boviously, it's not there, unless you're dual-booting