Is the first khul' valid, and does it count as a divorce? Is the marriage contract valid without a guardian or witnesses? Do subsequent divorces count? And is the last khul' valid without compensation?

If the wife requests Khul' (divorce by mutual agreement, often involving compensation from the wife), and an agreement is reached, the Khul' is effective and does not require a ruling from a Sharia court. Marriage without a guardian (wali) or witnesses is invalid according to the consensus of the four schools of thought, contrary to Dawud al-Zahiri who deems it valid. Talaq (divorce) occurs in a marriage whose validity is disputed. Therefore, if you divorced your wife twice after the first Khul', she has become irrevocably divorced from you (baynunah kubra), and she is not lawful for you until she marries another husband, as Allah Almighty says: "And if he has divorced her [for the third time], then she is not lawful to him afterward until she marries another husband." The last Khul' is disregarded. It is important to preserve marital life and not expose it to weakness.