Did we all stand before God in spirits form before birth to attest to faith?

The first part of the question is correct. It is mentioned in the Qur'an that God held all mankind, prior to their arrival in this world, and accepted their acknowledgement of His Lordship as the only God in the universe. The Qur'anic verse states:

"Your Lord brought forth their offspring from the loins of the children of Adam, and called them to bear witness about themselves. (He said): 'Am I not your Lord?' They replied: 'yes, indeed, we bear witness to that.' (This He did) lest you should say on the Day of Resurrection, 'We were truly unaware of this;' or lest you say, 'It was our forefathers who, in times gone by, associated partners with God, and we were only their late offspring. Will You destroy us on account of what those inventors of falsehood did?'" (Al-A'araf"7:172-173)

How and where did this happen are questions that we have no answer for. Its purpose, however, was to make us naturally inclined to believing in God and His Oneness. This is something that we feel in our nature. Of course there will always be individuals who deny God and refuse to believe in anyway, but these are the exception, not the rule.

As for the rest of the question, concerning the deposit of this acknowledgement in the Black Stone or giving the information to any human being, these are untrue. There is definitely nothing in the Qur'an about either point, nor is there any authentic Hadith to this effect. Hence, we reject this outright.