Is a marriage conducted online, with the statement "I accept So-and-So as a husband before God," without witnesses being present and the wife requesting to remove her veil before him, considered a valid and legitimate marriage?

This is not a marriage but a deviation, and calling it a marriage is a lie and a deception. It is obligatory to cut off the relationship with this man who trifles with the rulings of Allah, for claiming marriage to him permits what is unlawful and opens the door to blackmail. A correct marriage must include a guardian for the woman and two just witnesses, and any marriage without a guardian is void. "Any woman who marries herself without the permission of her guardian, her marriage is void, her marriage is void, her marriage is void." We advise you to cut off all ties with him and make sincere repentance.