Possibly related to the new verified-users, unverified-users groups. If your forum had the require email confirmation setting on and you upgraded then registered-users no longer have posting privileges. This is done by the upgrade scripts. But if you reverted without doing a database restore then registered-users won't have the privileges back.
New topic on mobile
When composing a new post (creating a new topic, or replaying) the buttons on the toolbar doesn't respond (only the last two of them, the question mark and the poll).
Furthermore the tag icon is shown instead the smiley icon that is shown on PC layout.
Here's an screenshot (android 5.0.1 lollipop):
I checked the behaviour of the buttons in PC and it is ok.