Which is why we were asking if anyone knows how to export or alter the database to go from utf8mb4 back to utf8.
Right. You can't actually do that. If you have 4 byte characters in the database, then going backwards to a character set that doesn't support them properly will cause your text to be truncated at the unsupported characters. And if you've been developing with 4.2, then you probably do have 4 byte characters somewhere.
You could go through and manually remove those characters, if you like. But it would probably take less time to copy and paste your text into the live site instead. Or do a normal WordPress export/import operation. Something like that.
Like I said earlier, if you want to edit your export files and change the collation with a search/replace, you can try it. No idea if it will work on your data though.