What is the ruling on a marriage that was based on the assumption that the wife was a virgin, then it became apparent that she was not, and is it considered void? Are the previous years of marriage considered unlawful, and what should she do after her repentance?

This marriage is valid, and your relationship with your husband is lawful. It is obligatory for you to conceal what happened from your husband and others. You must seek forgiveness and repent from committing the indecency and from hymenoplasty. The marriage of a previously married woman as if she were a virgin does not affect the validity of the contract, but the husband may have the option to annul the marriage if he stipulated virginity. If he did not stipulate that, then disclosure is not obligatory; rather, concealment is preferable. Your marriage is valid because of your repentance from indecency, and it is not permissible to inform your husband of what occurred. You must conceal yourself with the concealment of Allah and increase in repentance, seeking forgiveness, and righteous deeds. The hymenoplasty procedure is not permissible, but repentance nullifies what came before it.