As for speaking in tongues but being unsaved...
I was taught that the devil can imitate everything God can do EXCEPT make a person live right. Speaking in tongues is the initial evidence but if life changes do not follow then there is something wrong.
I have seen people who could jump, shout, speak in beautiful tongues, but were cheating on their husbands.
I've heard this referred to as "having the UNholy ghost."
And
Acts 2:38 says baptism is for remission ...so anyone who believes the Bible should have zero argument with that.