Is it permissible for a customary marriage to take place without the father's knowledge, and is it permissible to swear by triple divorce upon the wife in a customary contract without the father's knowledge of the marriage, considering that the wife is a virgin and under eighteen years of age?

It is not permissible to marry off a woman without her father's direct involvement or his deputization, as long as he is fit for guardianship. For the marriage of a woman without a guardian is invalid according to the majority of scholars. And divorce takes effect in a marriage over which there is a difference of opinion, such as a marriage without a guardian.