Giving the buyer a gift for purchasing over a certain amount

Q: A website is selling books at a discounted price. Whoever buys books for more than R250 gets a free bookmark. Whoever buys books for more than R750 gets another book free. Whoever buys books for more than R1499 gets free home delivery.

I want to know if transactions like these are valid where the seller gives a gift if the buyer buys products of a certain amount of money?

Seeking repentance for one's past sins before marriage

Q: If a man and woman commit zina before getting married. After their marriage, they had children and realized that what they have done before marriage was a sin. But they do not repent when being married because they dont have knowlegde that before marriage they had to repent.

After 6 years they got to know that they should have repented before nikaah, otherwise their nikaah is invalid. Is their nikaah valid or not as they repented after 6 years of marriage.