I can't really tell if you want to discuss these points or not. I will give a brief answer to the first one, because I am not sure if you are reading my answers.
You seem to be saying that you believe that the scriptures present the speaking in tongues as a sign to unbelievers that when they see it they will believe?
This is not what Paul meant when he quoted Isaiah.
21It is written in the law,
I will speak to this people
by people of other tongues
and by the lips of foreigners,
and even then, they will not listen to me,
a b
says the Lord.
22Speaking in tongues, then, is intended as a sign, not for believers but for unbelievers, while prophecy is not for unbelievers but for believers.
23If, therefore, the whole church assembles together and all are speaking in tongues and people who are outsiders or unbelievers come in, will they not say that you are out of your minds?
24But if all are prophesying and some unbeliever or outsider comes in, he is convicted by all and is called to account by all.
25The secrets of his heart will be revealed, and as a result he will fall facedown and worship God, proclaiming, “God is really among you.”
If you pay attention to the text he is saying that even though He would give them this prophesied miracle they still will not believe so that when he says that it is a sign for unbelievers it means it is a sign of judgment that the unbelievers will be without excuse in the day of judgment.
Then he goes on to show how prophesy will cause an
unbeliever to fall down and repent and so your idea that tongues would do this is not what Paul said at all. Paul is saying that Prophesy will cause an unbeliever to repent not that tongues would do that. This prophesy would make an unbeliever a believer. Not tongues.
By stating that tongues is a sign for unbelievers without the associated quote from Isaiah you have made a mistake in how you interpreted Paul's intended meaning. Lots of people do it. It is one of the least understood verse on this topic. It is easy to understand if quoted with the Isaiah context.
I did not say all of a sudden in this day no one can understand them. I said that Paul said in 1 Cor 14:2 that no man can understand them and that they are not speaking to man but to God.
And yes, 1 Cor 12 - 14 does show us that at that time they were to speak in tongues as the Spirit gave the utterance 2 or 3 at the most taking turns and only with interpretation to edify the saints when they met together in the assembly. I think we all agree that was a the positive part that was a good thing. So yes, doing that same thing in the assembly today would be biblical. And match what they did. It's not complicated. It does require faith. As do all good things from God.