Board Thread:Shadow Fight 2 Discussion/@comment-118.100.209.239-20160717090741/@comment-25669516-20181019123727

You might not have hacked it yourself but you are using a modified version of the apk. Of course it will not work in online mode. Just be happy Nekki hasn't banned your account straight away.

As for who the last boss is, there isn't much information available regarding him at the moment. SF2 has not had any major content updates since Feb-March of this year.