I can't find the dual option on iOS
In the screenshots of the app there is an option to dual at the bottom of the page... I ain't got that?! Just a big blue bar that says practice weak skills. Do I have to unlock duals or am I missing something?
What version of iOS are you using and do you have the latest version of duolingo?
If you are using an old iOS or an old version of duolingo, you may not have the option.
....and you have an iPhone correct? I don't know then. Perhaps they are testing a feature where they don't offer it, although this doesn't sound likely to me.
You should probably move this discussion to the troubleshooting forum (edit, post to: troubleshooting)
I think they're just offering that layout without dueling (maybe they couldn't find a way to incorporate it into that version?).
I think he has the latest version (I have the same exact version [according to what he's describing] of the Duolingo app, one blue button at the bottom saying "Practice Weak Skills", no dueling feature) of Duolingo. I would post a screenshot of my profile to show you, but can't right now.
EDIT: Found a picture of the version he's describing (slightly different, though): http://i.imgur.com/0aWDrQl
Unfortunately, you can't unlock duels. I have the exact same version as you do (there's a big blue button at the bottom that says "Practice Weak Skills", and no option to duel) and I think there's absolutely no way to unlock or get to the dueling feature. Sorry! :(
But, you can make another account for duels (some accounts have different layouts)... but first you're going to have to do a few lessons before the feature becomes available.
Bummer! Maybe it will come in an update?! Seems odd that it's in the photos tho