On mobile, I cannot update any changes to my profile. The error that occurs is I have to choose an option for the privacy of my birthday, but whenever I choose that, no options come up.
It's not a big deal, I'll just get to the full site sometime. Just a heads up.
We know the mobile skin is pretty much broken but there's nothing we can do to fix it. It's a plugin and, short of minor visual changes, we can't control how it works. The author has been claiming for a long time now that a new version is on its way but I'm not optimistic at this point. Unfortunately, even in its current state, it's still the best option so for now, just continuing using the full site for things that don't work on the mobile one.
There's a planned update for MyBB that should come eventually that will rectify most problems.