Is the aforementioned misyar marriage void and considered adultery, given that the contract was written by the husband, witnessed by one witness, and the offer and acceptance were made over the phone between the husband and the wife's guardian, with the wife and the witness present and hearing?

If the offer and acceptance occur between the woman's guardian (wali) or his agent, and the husband or his agent, in the presence of two witnesses, then the marriage contract is valid. Many contemporary scholars are of the opinion that a marriage contract via telephone or similar means is not valid. A marriage contract is not valid with only one witness according to the majority of scholars, but as long as the couple believed the marriage to be valid, it is not considered zina (fornication), and the lineage of children and inheritance are established through it. It is recommended to renew the marriage contract in the presence of two witnesses, or to appoint someone else as an agent if meeting in person is difficult. Documenting the marriage contract and registering it with official authorities is necessary to avoid harms and the loss of rights.