I visited the Apple Store today and they said they have nothing to do to save your iPhone. Downgrade from iOS 11 to iOS 10 is IMPOSSIABLE. I figure a way to make your iPhone back to work, just simplily download an image from the downloads and restore your iPhone back to iOS 11. I haven't tried iOS 10.3.3 beta 4 but I am certainly sure that you can save your iPhone by using this way.
Ways to save your iPhone if you downgrade
I did this a few weeks ago after hating Beta 1 and now I cannot sync anything to the phone via iTunes or Apple Music...
Where is the file now for 10.3.3? I can't find it.